javascript suppress error and continue in for loop - javascript

I'm trying to implement a speedtest by downloading 3 image files from the internet, and averaging the time it took to load them. If there is an error for whatever reason, I want to skip loading that image and proceed with the next one. If the error occurs on the last image, then I want to calculate the average speed at that point and return to the caller.
Right now, once an error occurs (I deliberately changed the url of an image so it doesn't exist), it won't go further. I've tried returning true from the .onerror function, but no luck. Any suggestions?
var images = [{
"url": 'http://<removed>250k.jpg?n=' + Math.random(),
"size": 256000
}, {
"url": 'http://<removed>500k.jpg?n=' + Math.random(),
"size": 512000
}, {
"url": '<removed>1000k.jpg?n=' + Math.random(),
"size": 1024000
}
];
function calculateBandwidth() {
var results = [];
for (var i = 0; i < images.length; i++) {
var startTime, endTime;
var downloadSize = images[i].size;
var download = new Image();
download.onload = function () {
endTime = (new Date()).getTime();
var duration = (endTime - startTime) / 1000;
var bitsLoaded = downloadSize * 8;
var speedBps = (bitsLoaded / duration).toFixed(2);
var speedKbps = (speedBps / 1024).toFixed(2);
var speedMbps = (speedKbps / 1024).toFixed(2);
results.push(speedMbps);
//Calculate the average speed
if (results.length == 3) {
var avg = (parseFloat(results[0]) + parseFloat(results[1]) + parseFloat(results[2])).toFixed(2);
return avg;
}
}
download.onerror = function (e) {
console.log("Failed to load image!");
return true;
};
startTime = (new Date()).getTime();
download.src = images[i].url;
}
}

I think what you're not doing is controlling the process as each event occurs. Each onerror and onload tells you that the process stopped, not that it should quit per se. You initialize one image, it doesn't load, maybe take note, otherwise continue.
The thing is, you do the same thing at the end of onload too. That is, do whatever measurements, then move to the next or, if no more, run the script that cleans up and reports or whatnot.
For instance:
var site = 'http://upload.wikimedia.org/',
imgs = [
'wikipedia/commons/6/6e/Brandenburger_Tor_2004.jpg',
'wikipedia/commons/a/ad/Cegonha_alsaciana.jpg',
'wikipe/Cegonha_alsaciana.jpg',
'wikipedia/commons/d/da/CrayonLogs.jpg',
'wikipedia/commons/1/17/Bobbahn_ep.jpg',
'wikipedia/commons/9/90/DS_Citro%C3%ABn.jpg',
'wikipedia/commons/f/f0/DeutzFahr_Ladewagen_K_7.39.jpg',
'wikipedia/commons/c/c7/DenglerSW-Peach-faced-Lovebird-20051026-1280x960.jpg',
'wikipedia/commons/4/4d/FA-18F_Breaking_SoundBarrier.jpg'
];
My array of images. Hint, wikipe/Cegonha_alsaciana.jpg won't load. Be forewarned, these are large and load slowly and I use a cache buster to keep them firing onloads.
getimg();
In the fiddle, this is all within a window.onload event handler, so when that gets called, this initializes the process. I don't have a setup phase, per se, or otherwise I might have called it init() or setup().
function getimg() {
var img = document.createElement('img'),
path = imgs.shift();
if (path) {
img.onload = loaded;
img.onerror = notloaded;
img.src = site + path + '?cach=bust' + Math.floor(Math.random() * 9999);
console.log('Loading ', img.src);
document.body.appendChild(img);
} else {
console.log('Finished loading images.');
}
function loaded(e) {
console.log('Loaded ', e.target.src);
next();
}
function notloaded(e) {
console.log('Not loaded ', e.target.src);
next();
}
function next() {
console.log(imgs.length, ' imgs left to load.');
getimg();
}
}
http://jsfiddle.net/userdude/vfTfP/
This does what you're trying to do, without the timing mechanism built-in. I can break things off into steps, actions and events, so that I can control the steps as necessary. In a basic way, your script should not run much differently.

Related

How to put a gif with Canvas

I'm creating a game, and in my game, when the HERO stay near the MONSTER, a gif will be showed, to scare the player. But I have no idea how to do this. I tried to put PHP or HTML code, but it doesn't works... The function is AtualizaTela2(). This is my main code:
<!DOCTYPE HTML>
<html>
<head>
<title>Hero's Escape Game</title>
<script language="JavaScript" type="text/javascript">
var objCanvas=null; // object that represents the canvas
var objContexto=null;
// Hero positioning control
var xHero=300;
var yHero=100;
// Monster positioning control
var xMonster=620;
var yMonster=0;
var imgFundo2 = new Image();
imgFundo2.src = "Images/Pista2.png";
var imgMonster = new Image();
imgMonster.src = "Images/Monster.png";
var imgHero = new Image();
imgHero.src = "Images/Hero.png";
function AtualizaTela2(){
if((xHero >= xMonster-10)&&(xHero <= xMonster + 10))
{
/*gif here*/
}
objContexto.drawImage(imgFundo2,0,0);
objContexto.drawImage(imgHero, xHero, yHero);
objContexto.drawImage(imgMonster, xMonster, yMonster);
function Iniciar(){
objCanvas = document.getElementById("meuCanvas");
objContexto = objCanvas.getContext("2d");
AtualizaTela2();
}
/* the function HeroMovement() and MonsterMovement() are not here */
}
</script>
</head>
<body onLoad="Iniciar();" onkeydown="HeroMovement(event);">
<canvas id="meuCanvas" width="1233"
height="507"
style="border:1px solid #000000;">
Seu browser não suporta o elemento CANVAS, atualize-se!!!
</canvas><BR>
</body>
</html>
This is the simplified code, because the real code is very big!
Thanks for the help! :)
Loading and playing GIF image to canvas.
Sorry answer exceeded size limit, had to remove much of the detailed code comments.
I am not going to go into details as the whole process is rather complicated.
The only way to get a GIF animated in canvas is to decode the GIF image in javascript. Luckily the format is not too complicated with data arranged in blocks that contain image size, color pallets, timing information, a comment field, and how frames are drawn.
Custom GIF load and player.
The example below contains an object called GIF that will create custom format GIF images from URLs that can play a GIF similar to how a video is played. You can also randomly access all GIF frames in any order.
There are many callbacks and options. There is basic usage information in comments and the code shows how to load the gif. There are functions to pause and play, seek(timeInSeconds) and seekFrame(frameNumber), properties to control playSpeed and much more. There are no shuttling events as access is immediate.
var myGif = GIF();
myGif.load("GIFurl.gif");
Once loaded
ctx.drawImage(myGif.image,0,0); // will draw the playing gif image
Or access the frames via the frames buffer
ctx.drawImage(myGif.frames[0].image,0,0); // draw frame 0 only.
Go to the bottom of the GIF object to see all the options with comments.
The GIF must be same domain or have CORS header
The gif in he demo is from wiki commons and contains 250+ frames, some low end devices will have trouble with this as each frame is converted to a full RGBA image making the loaded GIF significantly larger than the gif file size.
The demo
Loads the gif displaying the frames and frame count as loaded.
When loaded 100 particles each with random access frames playing at independent speeds and independent directions are displayed in the background.
The foreground image is the gif playing at the frame rate embedded in the file.
Code is as is, as an example only and NOT for commercial use.
const ctx = canvas.getContext("2d");
var myGif;
// Can not load gif cross domain unless it has CORS header
const gifURL = "https://upload.wikimedia.org/wikipedia/commons/a/a2/Wax_fire.gif";
// timeout just waits till script has been parsed and executed
// then starts loading a gif
setTimeout(()=>{
myGif = GIF(); // creates a new gif
myGif.onerror = function(e){
console.log("Gif loading error " + e.type);
}
myGif.load(gifURL);
},0);
// Function draws an image
function drawImage(image,x,y,scale,rot){
ctx.setTransform(scale,0,0,scale,x,y);
ctx.rotate(rot);
ctx.drawImage(image,-image.width / 2, -image.height / 2);
}
// helper functions
const rand = (min = 1, max = min + (min = 0)) => Math.random() * (max - min) + min;
const setOf =(c,C)=>{var a=[],i=0;while(i<c){a.push(C(i++))}return a};
const eachOf =(a,C)=>{var i=0;const l=a.length;while(i<l && C(a[i],i++,l)!==true);return i};
const mod = (v,m) => ((v % m) + m) % m;
// create 100 particles
const particles = setOf(100,() => {
return {
x : rand(innerWidth),
y : rand(innerHeight),
scale : rand(0.15, 0.5),
rot : rand(Math.PI * 2),
frame : 0,
frameRate : rand(-2,2),
dr : rand(-0.1,0.1),
dx : rand(-4,4),
dy : rand(-4,4),
};
});
// Animate and draw 100 particles
function drawParticles(){
eachOf(particles, part => {
part.x += part.dx;
part.y += part.dy;
part.rot += part.dr;
part.frame += part.frameRate;
part.x = mod(part.x,innerWidth);
part.y = mod(part.y,innerHeight);
var frame = mod(part.frame ,myGif.frames.length) | 0;
drawImage(myGif.frames[frame].image,part.x,part.y,part.scale,part.rot);
});
}
var w = canvas.width;
var h = canvas.height;
var cw = w / 2; // center
var ch = h / 2;
// main update function
function update(timer) {
ctx.setTransform(1, 0, 0, 1, 0, 0); // reset transform
if (w !== innerWidth || h !== innerHeight) {
cw = (w = canvas.width = innerWidth) / 2;
ch = (h = canvas.height = innerHeight) / 2;
} else {
ctx.clearRect(0, 0, w, h);
}
if(myGif) { // If gif object defined
if(!myGif.loading){ // if loaded
// draw random access to gif frames
drawParticles();
drawImage(myGif.image,cw,ch,1,0); // displays the current frame.
}else if(myGif.lastFrame !== null){ // Shows frames as they load
ctx.drawImage(myGif.lastFrame.image,0,0);
ctx.fillStyle = "white";
ctx.fillText("GIF loading frame " + myGif.frames.length ,10,21);
ctx.fillText("GIF loading frame " + myGif.frames.length,10,19);
ctx.fillText("GIF loading frame " + myGif.frames.length,9,20);
ctx.fillText("GIF loading frame " + myGif.frames.length,11,20);
ctx.fillStyle = "black";
ctx.fillText("GIF loading frame " + myGif.frames.length,10,20);
}
}else{
ctx.fillText("Waiting for GIF image ",10,20);
}
requestAnimationFrame(update);
}
requestAnimationFrame(update);
/*============================================================================
Gif Decoder and player for use with Canvas API's
**NOT** for commercial use.
To use
var myGif = GIF(); // creates a new gif
var myGif = new GIF(); // will work as well but not needed as GIF() returns the correct reference already.
myGif.load("myGif.gif"); // set URL and load
myGif.onload = function(event){ // fires when loading is complete
//event.type = "load"
//event.path array containing a reference to the gif
}
myGif.onprogress = function(event){ // Note this function is not bound to myGif
//event.bytesRead bytes decoded
//event.totalBytes total bytes
//event.frame index of last frame decoded
}
myGif.onerror = function(event){ // fires if there is a problem loading. this = myGif
//event.type a description of the error
//event.path array containing a reference to the gif
}
Once loaded the gif can be displayed
if(!myGif.loading){
ctx.drawImage(myGif.image,0,0);
}
You can display the last frame loaded during loading
if(myGif.lastFrame !== null){
ctx.drawImage(myGif.lastFrame.image,0,0);
}
To access all the frames
var gifFrames = myGif.frames; // an array of frames.
A frame holds various frame associated items.
myGif.frame[0].image; // the first frames image
myGif.frame[0].delay; // time in milliseconds frame is displayed for
Gifs use various methods to reduce the file size. The loaded frames do not maintain the optimisations and hold the full resolution frames as DOM images. This mean the memory footprint of a decode gif will be many time larger than the Gif file.
*/
const GIF = function () {
// **NOT** for commercial use.
var timerID; // timer handle for set time out usage
var st; // holds the stream object when loading.
var interlaceOffsets = [0, 4, 2, 1]; // used in de-interlacing.
var interlaceSteps = [8, 8, 4, 2];
var interlacedBufSize; // this holds a buffer to de interlace. Created on the first frame and when size changed
var deinterlaceBuf;
var pixelBufSize; // this holds a buffer for pixels. Created on the first frame and when size changed
var pixelBuf;
const GIF_FILE = { // gif file data headers
GCExt : 0xF9,
COMMENT : 0xFE,
APPExt : 0xFF,
UNKNOWN : 0x01, // not sure what this is but need to skip it in parser
IMAGE : 0x2C,
EOF : 59, // This is entered as decimal
EXT : 0x21,
};
// simple buffered stream used to read from the file
var Stream = function (data) {
this.data = new Uint8ClampedArray(data);
this.pos = 0;
var len = this.data.length;
this.getString = function (count) { // returns a string from current pos of len count
var s = "";
while (count--) { s += String.fromCharCode(this.data[this.pos++]) }
return s;
};
this.readSubBlocks = function () { // reads a set of blocks as a string
var size, count, data = "";
do {
count = size = this.data[this.pos++];
while (count--) { data += String.fromCharCode(this.data[this.pos++]) }
} while (size !== 0 && this.pos < len);
return data;
}
this.readSubBlocksB = function () { // reads a set of blocks as binary
var size, count, data = [];
do {
count = size = this.data[this.pos++];
while (count--) { data.push(this.data[this.pos++]);}
} while (size !== 0 && this.pos < len);
return data;
}
};
// LZW decoder uncompressed each frames pixels
// this needs to be optimised.
// minSize is the min dictionary as powers of two
// size and data is the compressed pixels
function lzwDecode(minSize, data) {
var i, pixelPos, pos, clear, eod, size, done, dic, code, last, d, len;
pos = pixelPos = 0;
dic = [];
clear = 1 << minSize;
eod = clear + 1;
size = minSize + 1;
done = false;
while (!done) { // JavaScript optimisers like a clear exit though I never use 'done' apart from fooling the optimiser
last = code;
code = 0;
for (i = 0; i < size; i++) {
if (data[pos >> 3] & (1 << (pos & 7))) { code |= 1 << i }
pos++;
}
if (code === clear) { // clear and reset the dictionary
dic = [];
size = minSize + 1;
for (i = 0; i < clear; i++) { dic[i] = [i] }
dic[clear] = [];
dic[eod] = null;
} else {
if (code === eod) { done = true; return }
if (code >= dic.length) { dic.push(dic[last].concat(dic[last][0])) }
else if (last !== clear) { dic.push(dic[last].concat(dic[code][0])) }
d = dic[code];
len = d.length;
for (i = 0; i < len; i++) { pixelBuf[pixelPos++] = d[i] }
if (dic.length === (1 << size) && size < 12) { size++ }
}
}
};
function parseColourTable(count) { // get a colour table of length count Each entry is 3 bytes, for RGB.
var colours = [];
for (var i = 0; i < count; i++) { colours.push([st.data[st.pos++], st.data[st.pos++], st.data[st.pos++]]) }
return colours;
}
function parse (){ // read the header. This is the starting point of the decode and async calls parseBlock
var bitField;
st.pos += 6;
gif.width = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
gif.height = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
bitField = st.data[st.pos++];
gif.colorRes = (bitField & 0b1110000) >> 4;
gif.globalColourCount = 1 << ((bitField & 0b111) + 1);
gif.bgColourIndex = st.data[st.pos++];
st.pos++; // ignoring pixel aspect ratio. if not 0, aspectRatio = (pixelAspectRatio + 15) / 64
if (bitField & 0b10000000) { gif.globalColourTable = parseColourTable(gif.globalColourCount) } // global colour flag
setTimeout(parseBlock, 0);
}
function parseAppExt() { // get application specific data. Netscape added iterations and terminator. Ignoring that
st.pos += 1;
if ('NETSCAPE' === st.getString(8)) { st.pos += 8 } // ignoring this data. iterations (word) and terminator (byte)
else {
st.pos += 3; // 3 bytes of string usually "2.0" when identifier is NETSCAPE
st.readSubBlocks(); // unknown app extension
}
};
function parseGCExt() { // get GC data
var bitField;
st.pos++;
bitField = st.data[st.pos++];
gif.disposalMethod = (bitField & 0b11100) >> 2;
gif.transparencyGiven = bitField & 0b1 ? true : false; // ignoring bit two that is marked as userInput???
gif.delayTime = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
gif.transparencyIndex = st.data[st.pos++];
st.pos++;
};
function parseImg() { // decodes image data to create the indexed pixel image
var deinterlace, frame, bitField;
deinterlace = function (width) { // de interlace pixel data if needed
var lines, fromLine, pass, toline;
lines = pixelBufSize / width;
fromLine = 0;
if (interlacedBufSize !== pixelBufSize) { // create the buffer if size changed or undefined.
deinterlaceBuf = new Uint8Array(pixelBufSize);
interlacedBufSize = pixelBufSize;
}
for (pass = 0; pass < 4; pass++) {
for (toLine = interlaceOffsets[pass]; toLine < lines; toLine += interlaceSteps[pass]) {
deinterlaceBuf.set(pixelBuf.subarray(fromLine, fromLine + width), toLine * width);
fromLine += width;
}
}
};
frame = {}
gif.frames.push(frame);
frame.disposalMethod = gif.disposalMethod;
frame.time = gif.length;
frame.delay = gif.delayTime * 10;
gif.length += frame.delay;
if (gif.transparencyGiven) { frame.transparencyIndex = gif.transparencyIndex }
else { frame.transparencyIndex = undefined }
frame.leftPos = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
frame.topPos = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
frame.width = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
frame.height = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
bitField = st.data[st.pos++];
frame.localColourTableFlag = bitField & 0b10000000 ? true : false;
if (frame.localColourTableFlag) { frame.localColourTable = parseColourTable(1 << ((bitField & 0b111) + 1)) }
if (pixelBufSize !== frame.width * frame.height) { // create a pixel buffer if not yet created or if current frame size is different from previous
pixelBuf = new Uint8Array(frame.width * frame.height);
pixelBufSize = frame.width * frame.height;
}
lzwDecode(st.data[st.pos++], st.readSubBlocksB()); // decode the pixels
if (bitField & 0b1000000) { // de interlace if needed
frame.interlaced = true;
deinterlace(frame.width);
} else { frame.interlaced = false }
processFrame(frame); // convert to canvas image
};
function processFrame(frame) { // creates a RGBA canvas image from the indexed pixel data.
var ct, cData, dat, pixCount, ind, useT, i, pixel, pDat, col, frame, ti;
frame.image = document.createElement('canvas');
frame.image.width = gif.width;
frame.image.height = gif.height;
frame.image.ctx = frame.image.getContext("2d");
ct = frame.localColourTableFlag ? frame.localColourTable : gif.globalColourTable;
if (gif.lastFrame === null) { gif.lastFrame = frame }
useT = (gif.lastFrame.disposalMethod === 2 || gif.lastFrame.disposalMethod === 3) ? true : false;
if (!useT) { frame.image.ctx.drawImage(gif.lastFrame.image, 0, 0, gif.width, gif.height) }
cData = frame.image.ctx.getImageData(frame.leftPos, frame.topPos, frame.width, frame.height);
ti = frame.transparencyIndex;
dat = cData.data;
if (frame.interlaced) { pDat = deinterlaceBuf }
else { pDat = pixelBuf }
pixCount = pDat.length;
ind = 0;
for (i = 0; i < pixCount; i++) {
pixel = pDat[i];
col = ct[pixel];
if (ti !== pixel) {
dat[ind++] = col[0];
dat[ind++] = col[1];
dat[ind++] = col[2];
dat[ind++] = 255; // Opaque.
} else
if (useT) {
dat[ind + 3] = 0; // Transparent.
ind += 4;
} else { ind += 4 }
}
frame.image.ctx.putImageData(cData, frame.leftPos, frame.topPos);
gif.lastFrame = frame;
if (!gif.waitTillDone && typeof gif.onload === "function") { doOnloadEvent() }// if !waitTillDone the call onload now after first frame is loaded
};
// **NOT** for commercial use.
function finnished() { // called when the load has completed
gif.loading = false;
gif.frameCount = gif.frames.length;
gif.lastFrame = null;
st = undefined;
gif.complete = true;
gif.disposalMethod = undefined;
gif.transparencyGiven = undefined;
gif.delayTime = undefined;
gif.transparencyIndex = undefined;
gif.waitTillDone = undefined;
pixelBuf = undefined; // dereference pixel buffer
deinterlaceBuf = undefined; // dereference interlace buff (may or may not be used);
pixelBufSize = undefined;
deinterlaceBuf = undefined;
gif.currentFrame = 0;
if (gif.frames.length > 0) { gif.image = gif.frames[0].image }
doOnloadEvent();
if (typeof gif.onloadall === "function") {
(gif.onloadall.bind(gif))({ type : 'loadall', path : [gif] });
}
if (gif.playOnLoad) { gif.play() }
}
function canceled () { // called if the load has been cancelled
finnished();
if (typeof gif.cancelCallback === "function") { (gif.cancelCallback.bind(gif))({ type : 'canceled', path : [gif] }) }
}
function parseExt() { // parse extended blocks
const blockID = st.data[st.pos++];
if(blockID === GIF_FILE.GCExt) { parseGCExt() }
else if(blockID === GIF_FILE.COMMENT) { gif.comment += st.readSubBlocks() }
else if(blockID === GIF_FILE.APPExt) { parseAppExt() }
else {
if(blockID === GIF_FILE.UNKNOWN) { st.pos += 13; } // skip unknow block
st.readSubBlocks();
}
}
function parseBlock() { // parsing the blocks
if (gif.cancel !== undefined && gif.cancel === true) { canceled(); return }
const blockId = st.data[st.pos++];
if(blockId === GIF_FILE.IMAGE ){ // image block
parseImg();
if (gif.firstFrameOnly) { finnished(); return }
}else if(blockId === GIF_FILE.EOF) { finnished(); return }
else { parseExt() }
if (typeof gif.onprogress === "function") {
gif.onprogress({ bytesRead : st.pos, totalBytes : st.data.length, frame : gif.frames.length });
}
setTimeout(parseBlock, 0); // parsing frame async so processes can get some time in.
};
function cancelLoad(callback) { // cancels the loading. This will cancel the load before the next frame is decoded
if (gif.complete) { return false }
gif.cancelCallback = callback;
gif.cancel = true;
return true;
}
function error(type) {
if (typeof gif.onerror === "function") { (gif.onerror.bind(this))({ type : type, path : [this] }) }
gif.onload = gif.onerror = undefined;
gif.loading = false;
}
function doOnloadEvent() { // fire onload event if set
gif.currentFrame = 0;
gif.nextFrameAt = gif.lastFrameAt = new Date().valueOf(); // just sets the time now
if (typeof gif.onload === "function") { (gif.onload.bind(gif))({ type : 'load', path : [gif] }) }
gif.onerror = gif.onload = undefined;
}
function dataLoaded(data) { // Data loaded create stream and parse
st = new Stream(data);
parse();
}
function loadGif(filename) { // starts the load
var ajax = new XMLHttpRequest();
ajax.responseType = "arraybuffer";
ajax.onload = function (e) {
if (e.target.status === 404) { error("File not found") }
else if(e.target.status >= 200 && e.target.status < 300 ) { dataLoaded(ajax.response) }
else { error("Loading error : " + e.target.status) }
};
ajax.open('GET', filename, true);
ajax.send();
ajax.onerror = function (e) { error("File error") };
this.src = filename;
this.loading = true;
}
function play() { // starts play if paused
if (!gif.playing) {
gif.paused = false;
gif.playing = true;
playing();
}
}
function pause() { // stops play
gif.paused = true;
gif.playing = false;
clearTimeout(timerID);
}
function togglePlay(){
if(gif.paused || !gif.playing){ gif.play() }
else{ gif.pause() }
}
function seekFrame(frame) { // seeks to frame number.
clearTimeout(timerID);
gif.currentFrame = frame % gif.frames.length;
if (gif.playing) { playing() }
else { gif.image = gif.frames[gif.currentFrame].image }
}
function seek(time) { // time in Seconds // seek to frame that would be displayed at time
clearTimeout(timerID);
if (time < 0) { time = 0 }
time *= 1000; // in ms
time %= gif.length;
var frame = 0;
while (time > gif.frames[frame].time + gif.frames[frame].delay && frame < gif.frames.length) { frame += 1 }
gif.currentFrame = frame;
if (gif.playing) { playing() }
else { gif.image = gif.frames[gif.currentFrame].image}
}
function playing() {
var delay;
var frame;
if (gif.playSpeed === 0) {
gif.pause();
return;
} else {
if (gif.playSpeed < 0) {
gif.currentFrame -= 1;
if (gif.currentFrame < 0) {gif.currentFrame = gif.frames.length - 1 }
frame = gif.currentFrame;
frame -= 1;
if (frame < 0) { frame = gif.frames.length - 1 }
delay = -gif.frames[frame].delay * 1 / gif.playSpeed;
} else {
gif.currentFrame += 1;
gif.currentFrame %= gif.frames.length;
delay = gif.frames[gif.currentFrame].delay * 1 / gif.playSpeed;
}
gif.image = gif.frames[gif.currentFrame].image;
timerID = setTimeout(playing, delay);
}
}
var gif = { // the gif image object
onload : null, // fire on load. Use waitTillDone = true to have load fire at end or false to fire on first frame
onerror : null, // fires on error
onprogress : null, // fires a load progress event
onloadall : null, // event fires when all frames have loaded and gif is ready
paused : false, // true if paused
playing : false, // true if playing
waitTillDone : true, // If true onload will fire when all frames loaded, if false, onload will fire when first frame has loaded
loading : false, // true if still loading
firstFrameOnly : false, // if true only load the first frame
width : null, // width in pixels
height : null, // height in pixels
frames : [], // array of frames
comment : "", // comments if found in file. Note I remember that some gifs have comments per frame if so this will be all comment concatenated
length : 0, // gif length in ms (1/1000 second)
currentFrame : 0, // current frame.
frameCount : 0, // number of frames
playSpeed : 1, // play speed 1 normal, 2 twice 0.5 half, -1 reverse etc...
lastFrame : null, // temp hold last frame loaded so you can display the gif as it loads
image : null, // the current image at the currentFrame
playOnLoad : true, // if true starts playback when loaded
// functions
load : loadGif, // call this to load a file
cancel : cancelLoad, // call to stop loading
play : play, // call to start play
pause : pause, // call to pause
seek : seek, // call to seek to time
seekFrame : seekFrame, // call to seek to frame
togglePlay : togglePlay, // call to toggle play and pause state
};
return gif;
}
/*=========================================================================
End of gif reader
*/
const mouse = {
bounds: null,
x: 0,
y: 0,
button: false
};
function mouseEvents(e) {
const m = mouse;
m.bounds = canvas.getBoundingClientRect();
m.x = e.pageX - m.bounds.left - scrollX;
m.y = e.pageY - m.bounds.top - scrollY;
mouse.x = e.pageX;
m.button = e.type === "mousedown" ? true : e.type === "mouseup" ? false : m.button;
}
["down", "up", "move"].forEach(name => document.addEventListener("mouse" + name, mouseEvents));
canvas {
position: absolute;
top: 0px;
left: 0px;
}
<canvas id="canvas"></canvas>
NOTES
This works for 99% of gifs. Occasionally you will find a gif that does not play correctly. Reason: (I never bothered to find out). Fix: re-encode gif using modern encoder.
There are some minor inconsistencies that need fixing. In time I will provide a codePen example with ES6 and improved interface. Stay tuned.
Here ya go:
You will need to exctract each frames and make an array out of them
split frames: http://gifgifs.com/split/
easier if you have urls or path like http://lol.com/Img1.png ...... http://lol.com/Img27.png with which you can do a simple loop like this:
var Img = [];
for (var i = 0; i < 28; i++) {
Img[i] = new Image();
Img[i].src = "http://lol.com/Img"+i+".png";
}
function drawAnimatedImage(arr,x,y,angle,factor,changespeed) {
if (!factor) {
factor = 1;
}
if (!changespeed) {
changespeed = 1;
}
ctx.save();
ctx.translate(x, y);
ctx.rotate(angle * Math.PI / 180);
if (!!arr[Math.round(Date.now()/changespeed) % arr.length]) {
ctx.drawImage(arr[Math.round(Date.now()/changespeed) % arr.length], -(arr[Math.round(Date.now()/changespeed) % arr.length].width * factor / 2), -(arr[Math.round(Date.now()/changespeed) % arr.length].height * factor / 2), arr[Math.round(Date.now()/changespeed) % arr.length].width * factor, arr[Math.round(Date.now()/changespeed) % arr.length].height * factor);
}
ctx.restore();
}
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext('2d');
var waitingWolf = [];
var url = ["https://i.imgur.com/k3T7psX.gif","https://i.imgur.com/CTSC8FC.gif","https://i.imgur.com/6NHLWKK.gif","https://i.imgur.com/U1u04sY.gif","https://i.imgur.com/4695vnQ.gif","https://i.imgur.com/oDO0YWT.gif","https://i.imgur.com/LqptRh1.gif","https://i.imgur.com/6gTxvul.gif","https://i.imgur.com/ULN5mqK.gif","https://i.imgur.com/RACB9WM.gif","https://i.imgur.com/4TZ6kNi.gif","https://i.imgur.com/9VvlzhK.gif","https://i.imgur.com/nGUnsfW.gif","https://i.imgur.com/2h8vLjK.gif","https://i.imgur.com/ZCdKkF1.gif","https://i.imgur.com/wZmWrYP.gif","https://i.imgur.com/4lhjVSz.gif","https://i.imgur.com/wVO0PbE.gif","https://i.imgur.com/cgGn5tV.gif","https://i.imgur.com/627gH5Y.gif","https://i.imgur.com/sLDSeS7.gif","https://i.imgur.com/1i1QNAs.gif","https://i.imgur.com/V3vDA1A.gif","https://i.imgur.com/Od2psNo.gif","https://i.imgur.com/WKDXFdh.gif","https://i.imgur.com/RlhIjaM.gif","https://i.imgur.com/293hMnm.gif","https://i.imgur.com/ITm0ukT.gif"]
function setup () {
for (var i = 0; i < 28; i++) {
waitingWolf[i] = new Image();
waitingWolf[i].src = url[i];
}
}
setup();
function yop() {
ctx.clearRect(0,0,1000,1000)
if (waitingWolf.length == 28) {
drawAnimatedImage(waitingWolf,300,100,0,1,60)
}
requestAnimationFrame(yop);
}
requestAnimationFrame(yop);
<canvas id="myCanvas" width="1000" height="1000">
</canvas>
You can use Gify & gifuct-js projects on Github.
First, download your Animated gif and prepare the images you need to do this on page load.
var framesArray;
var currentFrame = 0;
var totalFrames = null;
var oReq = new XMLHttpRequest();
oReq.open("GET", "/myfile.gif", true);
oReq.responseType = "arraybuffer";
oReq.onload = function (oEvent) {
var arrayBuffer = oReq.response; // Note: not oReq.responseText
if(gify.isAnimated(arrayBuffer)){
var gif = new GIF(arrayBuffer);
framesArray = gif.decompressFrames(true);
totalFrames = framesArray.length;
}
};
oReq.send(null);
When you want your animation to show so in your draw loop
if((xHero >= xMonster-10)&&(xHero <= xMonster + 10)){
// you need to work out from your frame rate when you should increase current frame
// based on the framerate of the gif image using framesArray[currentFrame].delay
// auto-detect if we need to jump to the first frame in the loop
// as we gone through all the frames
currentFrame = currentFrame % totalFrames;
var frame = framesArray[currentFrame];
var x,y;
// get x posstion as an offset from xHero
// get y posstion as an offset from yHero
objContexto.putImageData(frame.patch,x,y);
}
Please note this code is not tested I built following the documentation of the 2 projects so it might be a little wrong but it shows roughly how it is possible,
the 3rd link is the online contents of the demo folder for the gitfuct-js library
https://github.com/rfrench/gify
https://github.com/matt-way/gifuct-js
http://matt-way.github.io/gifuct-js/
It is not possible to simply draw a .gif (animated!) on the <canvas> element.
You have two options.
a) you can append the HTML with a <div> to which you append the .gif (via <img> node) and then layer the via z-Index and css top/left over the <canvas>, at the correct position. It will mess up with mouse events eventually tho, which can be solved by event propagation. I would consider this a poor mans solution.
b) You need to learn how to animate stuff. Look up window.requestAnimationFrame method. Doing so will allow you to animate on the <canvas>, which can emulate the .gif behavior you are looking for. It will however be a bit complex at your current level i think.
You can draw the .gif on the canvas like the above poster described. However, it will be 100 % static, like a .jpg or .png in that case, unless you manage to dissolve the .gif into its frames and still use the window.requestAnimationFrame method.
Basicly, if you want the animated behavior of a .gif, you will need to make major adjustments.
Simply draw your image on the canvas at whatever position you want to insert your gif. I'll assume you want to insert your gif in the canvas meuCanvas.
So:
if((xHero >= xMonster-10)&&(xHero <= xMonster + 10))
{
var ctx = document.getElementById('meuCanvas').getContext('2d');
var img = new Image();
img.onload = function() {
ctx.drawImage(img, 0, 0);
};
img.src = 'http://media3.giphy.com/media/kEKcOWl8RMLde/giphy.gif';
}
I'm also not quite sure what your problem is, but instead of:
if((xHero >= xMonster-10)||(xHero <= xMonster + 10))
{
/*gif here*/
}
you probably want:
if (xHero >= xMonster-10 && xHero <= xMonster + 10)
{
/*gif here*/
}
|| means OR
&& means AND
In your code using OR makes the condition always true; that's probably not what you want.

Black images from canvas.toDataURL()

I have created a web application where users can upload images from their filesystem but in few cases I only get black image data on the server side. I have never got this issue in my development environment on lan even with the original images causing the error. This failure occurs overall only sporadic but especially one user is affected. All users should work with the latest firefox. I have read most of the question about this topic and I dont think this is related to a security issue, the jpg/png setting or preserveDrawingBuffer. Because I have never got this problem on lan with a fast PC and the fact that often the last selected images are affected it seems to be a synchronization problem.
To avoid this I work with $.Deferred and Callbacks but may be I missed something. First I load and convert the selected images directly into a list of canvas. The upload is disabled until this is finished. During the upload I just loop through the canvas list and read the data (canvas.toDataURL()) with a $.Deferred and transfer it to the server via ajax.
Get the images to the page:
var file = document.getElementById('fileSelect');
if (file != undefined) {
file.onchange = function (e) {
btnUpload.SetEnabled(false);
loadImgs(e, function () {
btnUpload.SetEnabled(true);
});
};
}
function loadImgs(e, callback) {
for (var t = 0; t < e.target.files.length; t++) {
if ($('.CanvasClass').length <= 20) {
var myTmpImg = new Image();
var myName = e.target.files[t].name;
myTmpImg.src = URL.createObjectURL(e.target.files[t]);
myTmpImg.onload = function () {
var GrenzeX = 1024;
var GrenzeY = 768;
var myFactor = 1;
if (myTmpImg.naturalWidth > GrenzeX || myTmpImg.naturalHeight > GrenzeY) {
if ((GrenzeX / myTmpImg.naturalWidth) < (GrenzeY / myTmpImg.naturalHeight)) {
myFactor = GrenzeX / myTmpImg.naturalWidth;
} else {
myFactor = GrenzeY / myTmpImg.naturalHeight;
}
}
var myCanvas = document.createElement('canvas');
myCanvas.className = "CanvasClass";
myCanvas.height = this.naturalHeight * myFactor;
myCanvas.width = this.naturalWidth * myFactor;
var ctx = myCanvas.getContext("2d");
ctx.drawImage(this, 0, 0, myCanvas.width, myCanvas.height);
$("#myImages").append(myCanvas);
myMetaData.push(new newImgData('', '', myName));
}
}
}
if (callback && typeof callback == "function") {
callback();
}
}
Read and transfer the Data:
$('.CanvasClass').each(function () {
var fd = new FormData();
var base64Data = getBase64Image(this, false);
base64Data.then(function (result) {
//Create Ajax Request
});
});
function getBase64Image(myCanvas, modus) {
var deferred = $.Deferred();
var dataURL = myCanvas.toDataURL("image/jpeg", 0.9);
if (modus === true) {
deferred.resolve(dataURL);
} else {
deferred.resolve(dataURL.replace(/^data:image\/(png|jpeg);base64,/, ""));
}
return deferred.promise();
}
I can also exclude issues during the data transfer because I logged the size of the images on clientside before uploading and compared this to the data at serverside and it was the same.

Changing images using delays

I’m trying to figure out how to make an animation using the order of three images.
The default image is “image1.png” that always shows when the page loads.
After every 5 seconds, the variable “back.src” must abruptly change
to image2.png, so without fading. The default is image1.png
And then after 0.5 seconds, the variable again changes but then to
image3.png.
0.5 seconds later it changes back to image2.png
and 0.5 later again back to image1.png.
This is to be repeated in a loop because I want to repeat the process again after 5 seconds.
My problem is, I don't know if structuring this code is the best way to go about it. How would my code need to look based on the requirement explained above?
Here's my code of what I've got so far:
var back = new Image();
back.src = "image1.png";
function wait(miliseconds) {
var currentTime = new Date().getTime();
while (currentTime + miliseconds >= new Date().getTime()) {
}
}
function image1() {
wait(5000);
back.src = "image2.png";
}
function image2() {
wait(500);
back.src = "image3.png";
}
function image3() {
wait(500);
back.src = "image2.png";
}
function animate(){
ctx.save();
ctx.clearRect(0, 0, cW, cH);
ctx.drawImage(back,0,0);
ctx.restore();
}
var animateInterval = setInterval(animate, 30);
There is no wait() operation in Javascript and usually trying to make one like you are doing causes bad things to happen (event loops get starved, user interfaces get locked up, etc...). Instead, you schedule things to run in the future with setTimeout(). This allows the JS engine to do other things (like service other events happening in the system) while you are waiting for your next loop iteration and is generally very important in Javascript.
I'd suggest you just put the sequence you want into a data structure and then use a timer that iterates through the data structure, wrapping when it gets to the end:
var data = [
["image1.png", 5000],
["image2.png", 500],
["image3.png", 500],
["image4.png", 500]
];
function runAnimation() {
var index = 0;
function animate(image){
ctx.save();
ctx.clearRect(0, 0, cW, cH);
ctx.drawImage(image,0,0);
ctx.restore();
}
function next() {
var img = new Image();
img.src = data[index][0];
animate(img);
// schedule next iteration
var t = data[index][1];
// increment and wrap index if past end
index = (index + 1) % data.length;
setTimeout(next, t);
}
next();
}
To make this work properly, you will need your images to be precached so they get loaded immediately. If you aren't going to precache the images, then you will need to add onload handlers so you can know when the images have finished loading and are ready for drawing.
There is info on precaching images here: How do you cache an image in Javascript
Or, to make sure your images are loaded before drawing with them, you can use an onload handler like this:
var data = [
["image1.png", 5000],
["image2.png", 500],
["image3.png", 500],
["image4.png", 500]
];
function runAnimation() {
var index = 0;
function animate(image){
ctx.save();
ctx.clearRect(0, 0, cW, cH);
ctx.drawImage(image,0,0);
ctx.restore();
}
function next() {
var img = new Image();
var nextSrc = data[index][0];
img.onload = function() {
animate(img);
// schedule next iteration
var t = data[index][1];
// increment and wrap index if past end
index = (index + 1) % data.length;
setTimeout(next, t);
};
img.src = nextSrc;
}
next();
}
You can achieve it using setIterval()
Read about JS Timers Here
Here is what you need : https://jsfiddle.net/nfe81zou/3/
var image1 = "https://pixabay.com/static/uploads/photo/2016/06/17/13/02/duck-1463317_960_720.jpg";
var image2 = "https://pixabay.com/static/uploads/photo/2013/09/22/16/56/duck-185014_960_720.jpg";
var image3 = "https://pixabay.com/static/uploads/photo/2013/11/02/03/23/ducks-204332_960_720.jpg";
$(function() {
$("#image").prop("src", image1);
setInterval(function() {
$("#image").prop("src", image2);
setTimeout(function() {
$("#image").prop("src", image1);
setTimeout(function() {
$("#image").prop("src", image3);
}, 500);
setTimeout(function() {
$("#image").prop("src", image2);
}, 1000);
}, 1500);
}, 5000);
});
#image {
border: 2px solid red;
width: 400px;
height: 200px;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<img src="" id="image"/>
This would be my approach on this problem. The images are displayed in the order of
0 (5000ms) -> 1 (500ms) -> 2 (500ms) -> 1 (500ms) -> 0 (5000ms) ...
There is no setInterval() here. This code utilizes a pseudo recursive setTimeout() implementation.
var images = ["http://1.bp.blogspot.com/_ZRj5nlc3sp8/S-T7vOsypQI/AAAAAAAADBo/0kYfB8BM6zE/s320/beautiful+girl+pics+1.jpg",
"http://1.bp.blogspot.com/-w4UtHwbrqBE/ViNbJWhnmvI/AAAAAAAADtY/hGbRtz993Tg/s1600/face%2Bwallpapers%2B%25282%2529.jpg",
"http://2.bp.blogspot.com/-4kZ9Iu8QTws/ViNbL3S29fI/AAAAAAAADtw/QakqQE72N1w/s1600/face%2Bwallpapers%2B%25286%2529.jpg"],
imel = document.getElementById("photo");
function displayImages(idx,fwd){
var ms = 0;
idx = idx || 0; // we could also use the ES6 default value method.
if (idx === 0) {
fwd = !fwd; // when index becomes 0 switch the direction of the loop
ms = fwd ? 5000 // if backwards rearrange index and duration to 0.5 sec
: (idx = images.length - 2, 500);
} else ms = 500; // when index is not 0 set the duration to 0.5 sec
imel.src = images[idx];
fwd ? setTimeout(function(){displayImages(++idx % images.length,fwd)},ms)
: setTimeout(function(){displayImages(--idx,fwd)},ms);
}
displayImages();
<image id ="photo"></image>

How can I get an AudioBufferSourceNode's current time?

When working with audio elements (<audio>) or contexts(AudioContext), you can check their currentTime property to know exactly the play time of your buffer.
All of this is fine an dandy until I created multiple sources (or AudioBufferSourceNode) in a single AudioContext.
The sources could be played at different times, therefore I would need to know their corresponding currentTime's, to illustrate:
Some base code for you to work off:
buffer1 = [0,1,0]; //not real buffers
buffer2 = [1,0,1];
ctx = new AudioContext();
source1 = ctx.createBufferSourceNode();
source1.buffer = buffer1;
source1.connect(ctx.destination);
source1.start(0);
source2 = ctx.createBufferSourceNode();
source2.buffer = buffer2;
source2.connect(ctx.destination);
setTimeout(1000/*some time later*/){
source2.start(0);
}
setTimeout(1500/*some more time later*/){
getCurrentTime();
}
function getCurrentTime(){
/* magic */
/* more magic */
console.log("the sources currentTime values are obviously 1500 (source1) and 500 (source2).");
}
What I usually do is create a wrapper for the audio source node that keeps track of the playback state. I've tried to minimise the code below to show the basics.
The core idea is to keep track of the time the sound is started and the time the sound is 'paused' and use those values to get the current time and to resume playback from the paused position.
I put a working example on codepen
function createSound(buffer, context) {
var sourceNode = null,
startedAt = 0,
pausedAt = 0,
playing = false;
var play = function() {
var offset = pausedAt;
sourceNode = context.createBufferSource();
sourceNode.connect(context.destination);
sourceNode.buffer = buffer;
sourceNode.start(0, offset);
startedAt = context.currentTime - offset;
pausedAt = 0;
playing = true;
};
var pause = function() {
var elapsed = context.currentTime - startedAt;
stop();
pausedAt = elapsed;
};
var stop = function() {
if (sourceNode) {
sourceNode.disconnect();
sourceNode.stop(0);
sourceNode = null;
}
pausedAt = 0;
startedAt = 0;
playing = false;
};
var getPlaying = function() {
return playing;
};
var getCurrentTime = function() {
if(pausedAt) {
return pausedAt;
}
if(startedAt) {
return context.currentTime - startedAt;
}
return 0;
};
var getDuration = function() {
return buffer.duration;
};
return {
getCurrentTime: getCurrentTime,
getDuration: getDuration,
getPlaying: getPlaying,
play: play,
pause: pause,
stop: stop
};
}
Old thread (and very useful! thanks!) , but maybe worth mentioning that in the example above instead of
function update() {
window.requestAnimationFrame(update);
info.innerHTML = sound.getCurrentTime().toFixed(1) + '/' + sound.getDuration().toFixed(1);
}
update();
it may be more precise and less resource intensive to use a createScriptProcessor
like explained in this post
const audioBuffer = await audioContext.decodeAudioData(response.data);
const chan = audioBuffer.numberOfChannels;
const scriptNode = audioContext.createScriptProcessor(4096, chan, chan);
scriptNode.connect(audioContext.destination);
scriptNode.onaudioprocess = (e) => {
// ---> audio loop <----
};
[Update]
Note: As of the August 29 2014 Web Audio API spec publication, this feature has been marked as deprecated, and was replaced by AudioWorklet (see AudioWorkletNode). https://developers.google.com/web/updates/2017/12/audio-worklet

How to detect internet speed in JavaScript?

How can I create a JavaScript page that will detect the user’s internet speed and show it on the page? Something like “your internet speed is ??/?? Kb/s”.
It's possible to some extent but won't be really accurate, the idea is load image with a known file size then in its onload event measure how much time passed until that event was triggered, and divide this time in the image file size.
Example can be found here: Calculate speed using javascript
Test case applying the fix suggested there:
//JUST AN EXAMPLE, PLEASE USE YOUR OWN PICTURE!
var imageAddr = "http://www.kenrockwell.com/contax/images/g2/examples/31120037-5mb.jpg";
var downloadSize = 4995374; //bytes
function ShowProgressMessage(msg) {
if (console) {
if (typeof msg == "string") {
console.log(msg);
} else {
for (var i = 0; i < msg.length; i++) {
console.log(msg[i]);
}
}
}
var oProgress = document.getElementById("progress");
if (oProgress) {
var actualHTML = (typeof msg == "string") ? msg : msg.join("<br />");
oProgress.innerHTML = actualHTML;
}
}
function InitiateSpeedDetection() {
ShowProgressMessage("Loading the image, please wait...");
window.setTimeout(MeasureConnectionSpeed, 1);
};
if (window.addEventListener) {
window.addEventListener('load', InitiateSpeedDetection, false);
} else if (window.attachEvent) {
window.attachEvent('onload', InitiateSpeedDetection);
}
function MeasureConnectionSpeed() {
var startTime, endTime;
var download = new Image();
download.onload = function () {
endTime = (new Date()).getTime();
showResults();
}
download.onerror = function (err, msg) {
ShowProgressMessage("Invalid image, or error downloading");
}
startTime = (new Date()).getTime();
var cacheBuster = "?nnn=" + startTime;
download.src = imageAddr + cacheBuster;
function showResults() {
var duration = (endTime - startTime) / 1000;
var bitsLoaded = downloadSize * 8;
var speedBps = (bitsLoaded / duration).toFixed(2);
var speedKbps = (speedBps / 1024).toFixed(2);
var speedMbps = (speedKbps / 1024).toFixed(2);
ShowProgressMessage([
"Your connection speed is:",
speedBps + " bps",
speedKbps + " kbps",
speedMbps + " Mbps"
]);
}
}
<h1 id="progress">JavaScript is turned off, or your browser is realllllly slow</h1>
Quick comparison with "real" speed test service showed small difference of 0.12 Mbps when using big picture.
To ensure the integrity of the test, you can run the code with Chrome dev tool throttling enabled and then see if the result matches the limitation. (credit goes to user284130 :))
Important things to keep in mind:
The image being used should be properly optimized and compressed. If it isn't, then default compression on connections by the web server might show speed bigger than it actually is. Another option is using uncompressible file format, e.g. jpg. (thanks Rauli Rajande for pointing this out and Fluxine for reminding me)
The cache buster mechanism described above might not work with some CDN servers, which can be configured to ignore query string parameters, hence better setting cache control headers on the image itself. (thanks orcaman for pointing this out))
The bigger the image size is, the better. Larger image will make the test more accurate, 5 mb is decent, but if you can use even a bigger one it would be better.
Well, this is 2017 so you now have Network Information API (albeit with a limited support across browsers as of now) to get some sort of estimate downlink speed information:
navigator.connection.downlink
This is effective bandwidth estimate in Mbits per sec. The browser makes this estimate from recently observed application layer throughput across recently active connections. Needless to say, the biggest advantage of this approach is that you need not download any content just for bandwidth/ speed calculation.
You can look at this and a couple of other related attributes here
Due to it's limited support and different implementations across browsers (as of Nov 2017), would strongly recommend read this in detail
I needed a quick way to determine if the user connection speed was fast enough to enable/disable some features in a site I’m working on, I made this little script that averages the time it takes to download a single (small) image a number of times, it's working pretty accurately in my tests, being able to clearly distinguish between 3G or Wi-Fi for example, maybe someone can make a more elegant version or even a jQuery plugin.
var arrTimes = [];
var i = 0; // start
var timesToTest = 5;
var tThreshold = 150; //ms
var testImage = "http://www.google.com/images/phd/px.gif"; // small image in your server
var dummyImage = new Image();
var isConnectedFast = false;
testLatency(function(avg){
isConnectedFast = (avg <= tThreshold);
/** output */
document.body.appendChild(
document.createTextNode("Time: " + (avg.toFixed(2)) + "ms - isConnectedFast? " + isConnectedFast)
);
});
/** test and average time took to download image from server, called recursively timesToTest times */
function testLatency(cb) {
var tStart = new Date().getTime();
if (i<timesToTest-1) {
dummyImage.src = testImage + '?t=' + tStart;
dummyImage.onload = function() {
var tEnd = new Date().getTime();
var tTimeTook = tEnd-tStart;
arrTimes[i] = tTimeTook;
testLatency(cb);
i++;
};
} else {
/** calculate average of array items then callback */
var sum = arrTimes.reduce(function(a, b) { return a + b; });
var avg = sum / arrTimes.length;
cb(avg);
}
}
As I outline in this other answer here on StackOverflow, you can do this by timing the download of files of various sizes (start small, ramp up if the connection seems to allow it), ensuring through cache headers and such that the file is really being read from the remote server and not being retrieved from cache. This doesn't necessarily require that you have a server of your own (the files could be coming from S3 or similar), but you will need somewhere to get the files from in order to test connection speed.
That said, point-in-time bandwidth tests are notoriously unreliable, being as they are impacted by other items being downloaded in other windows, the speed of your server, links en route, etc., etc. But you can get a rough idea using this sort of technique.
Even though this is old and answered, i´d like to share the solution i made out of it 2020 base on Shadow Wizard Says No More War´s solution
I just merged it into an object that comes with the flexibility to run at anytime and run a callbacks if the specified mbps is higher or lower the measurement result.
you can start the test anywhere after you included the testConnectionSpeed Object by running the
/**
* #param float mbps - Specify a limit of mbps.
* #param function more(float result) - Called if more mbps than specified limit.
* #param function less(float result) - Called if less mbps than specified limit.
*/
testConnectionSpeed.run(mbps, more, less)
for example:
var testConnectionSpeed = {
imageAddr : "https://upload.wikimedia.org/wikipedia/commons/a/a6/Brandenburger_Tor_abends.jpg", // this is just an example, you rather want an image hosted on your server
downloadSize : 2707459, // Must match the file above (from your server ideally)
run:function(mbps_max,cb_gt,cb_lt){
testConnectionSpeed.mbps_max = parseFloat(mbps_max) ? parseFloat(mbps_max) : 0;
testConnectionSpeed.cb_gt = cb_gt;
testConnectionSpeed.cb_lt = cb_lt;
testConnectionSpeed.InitiateSpeedDetection();
},
InitiateSpeedDetection: function() {
window.setTimeout(testConnectionSpeed.MeasureConnectionSpeed, 1);
},
result:function(){
var duration = (endTime - startTime) / 1000;
var bitsLoaded = testConnectionSpeed.downloadSize * 8;
var speedBps = (bitsLoaded / duration).toFixed(2);
var speedKbps = (speedBps / 1024).toFixed(2);
var speedMbps = (speedKbps / 1024).toFixed(2);
if(speedMbps >= (testConnectionSpeed.max_mbps ? testConnectionSpeed.max_mbps : 1) ){
testConnectionSpeed.cb_gt ? testConnectionSpeed.cb_gt(speedMbps) : false;
}else {
testConnectionSpeed.cb_lt ? testConnectionSpeed.cb_lt(speedMbps) : false;
}
},
MeasureConnectionSpeed:function() {
var download = new Image();
download.onload = function () {
endTime = (new Date()).getTime();
testConnectionSpeed.result();
}
startTime = (new Date()).getTime();
var cacheBuster = "?nnn=" + startTime;
download.src = testConnectionSpeed.imageAddr + cacheBuster;
}
}
// start test immediatly, you could also call this on any event or whenever you want
testConnectionSpeed.run(1.5, function(mbps){console.log(">= 1.5Mbps ("+mbps+"Mbps)")}, function(mbps){console.log("< 1.5Mbps("+mbps+"Mbps)")} )
I used this successfuly to load lowres media for slow internet connections. You have to play around a bit because on the one hand, the larger the image, the more reasonable the test, on the other hand the test will take way much longer for slow connection and in my case I especially did not want slow connection users to load lots of MBs.
The image trick is cool but in my tests it was loading before some ajax calls I wanted to be complete.
The proper solution in 2017 is to use a worker (http://caniuse.com/#feat=webworkers).
The worker will look like:
/**
* This function performs a synchronous request
* and returns an object contain informations about the download
* time and size
*/
function measure(filename) {
var xhr = new XMLHttpRequest();
var measure = {};
xhr.open("GET", filename + '?' + (new Date()).getTime(), false);
measure.start = (new Date()).getTime();
xhr.send(null);
measure.end = (new Date()).getTime();
measure.len = parseInt(xhr.getResponseHeader('Content-Length') || 0);
measure.delta = measure.end - measure.start;
return measure;
}
/**
* Requires that we pass a base url to the worker
* The worker will measure the download time needed to get
* a ~0KB and a 100KB.
* It will return a string that serializes this informations as
* pipe separated values
*/
onmessage = function(e) {
measure0 = measure(e.data.base_url + '/test/0.bz2');
measure100 = measure(e.data.base_url + '/test/100K.bz2');
postMessage(
measure0.delta + '|' +
measure0.len + '|' +
measure100.delta + '|' +
measure100.len
);
};
The js file that will invoke the Worker:
var base_url = PORTAL_URL + '/++plone++experimental.bwtools';
if (typeof(Worker) === 'undefined') {
return; // unsupported
}
w = new Worker(base_url + "/scripts/worker.js");
w.postMessage({
base_url: base_url
});
w.onmessage = function(event) {
if (event.data) {
set_cookie(event.data);
}
};
Code taken from a Plone package I wrote:
https://github.com/collective/experimental.bwtools/blob/master/src/experimental/bwtools/browser/static/scripts/
It's better to use images for testing the speed. But if you have to deal with zip files, the below code works.
var fileURL = "your/url/here/testfile.zip";
var request = new XMLHttpRequest();
var avoidCache = "?avoidcache=" + (new Date()).getTime();;
request.open('GET', fileURL + avoidCache, true);
request.responseType = "application/zip";
var startTime = (new Date()).getTime();
var endTime = startTime;
request.onreadystatechange = function () {
if (request.readyState == 2)
{
//ready state 2 is when the request is sent
startTime = (new Date().getTime());
}
if (request.readyState == 4)
{
endTime = (new Date()).getTime();
var downloadSize = request.responseText.length;
var time = (endTime - startTime) / 1000;
var sizeInBits = downloadSize * 8;
var speed = ((sizeInBits / time) / (1024 * 1024)).toFixed(2);
console.log(downloadSize, time, speed);
}
}
request.send();
This will not work very well with files < 10MB. You will have to run aggregated results on multiple download attempts.
thanks to Punit S answer, for detecting dynamic connection speed change, you can use the following code :
navigator.connection.onchange = function () {
//do what you need to do ,on speed change event
console.log('Connection Speed Changed');
}
Improving upon John Smith's answer, a nice and clean solution which returns a Promise and thus can be used with async/await. Returns a value in Mbps.
const imageAddr = 'https://upload.wikimedia.org/wikipedia/commons/a/a6/Brandenburger_Tor_abends.jpg';
const downloadSize = 2707459; // this must match with the image above
let startTime, endTime;
async function measureConnectionSpeed() {
startTime = (new Date()).getTime();
const cacheBuster = '?nnn=' + startTime;
const download = new Image();
download.src = imageAddr + cacheBuster;
// this returns when the image is finished downloading
await download.decode();
endTime = (new Date()).getTime();
const duration = (endTime - startTime) / 1000;
const bitsLoaded = downloadSize * 8;
const speedBps = (bitsLoaded / duration).toFixed(2);
const speedKbps = (speedBps / 1024).toFixed(2);
const speedMbps = (speedKbps / 1024).toFixed(2);
return Math.round(Number(speedMbps));
}
I needed something similar, so I wrote https://github.com/beradrian/jsbandwidth. This is a rewrite of https://code.google.com/p/jsbandwidth/.
The idea is to make two calls through Ajax, one to download and the other to upload through POST.
It should work with both jQuery.ajax or Angular $http.
//JUST AN EXAMPLE, PLEASE USE YOUR OWN PICTURE!
var imageAddr = "https://i.ibb.co/sPbbkkZ/pexels-lisa-1540258.jpg";
var downloadSize = 10500000; //bytes
function ShowProgressMessage(msg) {
if (console) {
if (typeof msg == "string") {
console.log(msg);
} else {
for (var i = 0; i < msg.length; i++) {
console.log(msg[i]);
}
}
}
var oProgress = document.getElementById("progress");
if (oProgress) {
var actualHTML = (typeof msg == "string") ? msg : msg.join("<br />");
oProgress.innerHTML = actualHTML;
}
}
function InitiateSpeedDetection() {
ShowProgressMessage("Loading the image, please wait...");
window.setTimeout(MeasureConnectionSpeed, 1);
};
if (window.addEventListener) {
window.addEventListener('load', InitiateSpeedDetection, false);
} else if (window.attachEvent) {
window.attachEvent('onload', InitiateSpeedDetection);
}
function MeasureConnectionSpeed() {
var startTime, endTime;
var download = new Image();
download.onload = function () {
endTime = (new Date()).getTime();
showResults();
}
download.onerror = function (err, msg) {
ShowProgressMessage("Invalid image, or error downloading");
}
startTime = (new Date()).getTime();
var cacheBuster = "?nnn=" + startTime;
download.src = imageAddr + cacheBuster;
function showResults() {
var duration = (endTime - startTime) / 1000;
var bitsLoaded = downloadSize * 8;
var speedBps = (bitsLoaded / duration).toFixed(2);
var speedKbps = (speedBps / 1024).toFixed(2);
var speedMbps = (speedKbps / 1024).toFixed(2);
ShowProgressMessage([
"Your connection speed is:",
speedBps + " bps",
speedKbps + " kbps",
speedMbps + " Mbps"
]);
}
}
<h1 id="progress">JavaScript is turned off, or your browser is realllllly slow</h1>
Mini snippet:
var speedtest = {};
function speedTest_start(name) { speedtest[name]= +new Date(); }
function speedTest_stop(name) { return +new Date() - speedtest[name] + (delete
speedtest[name]?0:0); }
use like:
speedTest_start("test1");
// ... some code
speedTest_stop("test1");
// returns the time duration in ms
Also more tests possible:
speedTest_start("whole");
// ... some code
speedTest_start("part");
// ... some code
speedTest_stop("part");
// returns the time duration in ms of "part"
// ... some code
speedTest_stop("whole");
// returns the time duration in ms of "whole"

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