I'm developing my own portfolio website, which is based on JavaScript gallery. The script shows and prealoads images by tracking current position and it works brilliant when it comes to load only one filetype. Here comes extract:
var $current = 1;
var $sourceImage = 'path-to-images/'+$current+'.jpg';
var $newImage = new Image();
$newImage.src = $sourceImage;
But what if in the directory there are more than one filetype, for example: 1.jpg 2.jpg 3.gif 4.png ... ? What's the best way to find extension of file that exists on server and pass it to the variable?
Thanks for any advice.
To check if a file exists with JavaScript you have to send an ajax request:
var req = this.window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();
if (!req) {
throw new Error('XMLHttpRequest not supported');
}
// HEAD Results are usually shorter (faster) than GET
req.open('HEAD', url, false);
req.send(null);
if (req.status == 200) {
console.log('file exists');
}
else {
console.log('file does not exist');
}
from phpjs.
Your solutions are limited when only using Javascript. The simplest way is to have an array containing all of the file names,
var imageFiles = ["1.jpg", "2.jpg", "3.gif", "4.png"];
However, this may be undesirable if there are a large number of images.
Alternatively, you can write a page in PHP (or any language of your choice) that returns all the images in the directory as a JSON array.
["1.jpg", "2.jpg", "3.gif", "4.png"]
Then just use a framework such as jQuery to request the page; getJSON() would work nicely in this case. You can always reinvent the wheel, but I highly suggest a framework for AJAX.
Related
I've seen many partial answers to this here and elsewhere, but I am very much a novice coder and am hoping for a thorough solution. I have been able to set up recording audio from a laptop mic in Chrome Canary (v. 29.x) and can, using recorder.js, relatively easily set up recording a .wav file and saving that locally, a la:
http://webaudiodemos.appspot.com/AudioRecorder/index.html
But I need to be able to save the file onto a Linux server I have running. It's the actual sending of the blob recorded data to the server and saving it out as a .wav file that's catching me up. I don't have the requisite PHP and/or AJAX knowledge about how to save the blob to a URL and to deal, as I have been given to understand, with binaries on Linux that make saving that .wav file challenging indeed. I'd greatly welcome any pointers in the right direction.
Client side JavaScript function to upload the WAV blob:
function upload(blob) {
var xhr=new XMLHttpRequest();
xhr.onload=function(e) {
if(this.readyState === 4) {
console.log("Server returned: ",e.target.responseText);
}
};
var fd=new FormData();
fd.append("that_random_filename.wav",blob);
xhr.open("POST","<url>",true);
xhr.send(fd);
}
PHP file upload_wav.php:
<?php
// get the temporary name that PHP gave to the uploaded file
$tmp_filename=$_FILES["that_random_filename.wav"]["tmp_name"];
// rename the temporary file (because PHP deletes the file as soon as it's done with it)
rename($tmp_filename,"/tmp/uploaded_audio.wav");
?>
after which you can play the file /tmp/uploaded_audio.wav.
But remember! /tmp/uploaded_audio.wav was created by the user www-data, and (by PHP default) is not readable by the user. To automate adding the appropriate permissions, append the line
chmod("/tmp/uploaded_audio.wav",0755);
to the end of the PHP (before the PHP end tag ?>).
Hope this helps.
Easiest way, if you just want to hack that code, is go in to recorderWorker.js, and hack the exportWAV() function to something like this:
function exportWAV(type){
var bufferL = mergeBuffers(recBuffersL, recLength);
var bufferR = mergeBuffers(recBuffersR, recLength);
var interleaved = interleave(bufferL, bufferR);
var dataview = encodeWAV(interleaved);
var audioBlob = new Blob([dataview], { type: type });
var xhr=new XMLHttpRequest();
xhr.onload=function(e) {
if(this.readyState === 4) {
console.log("Server returned: ",e.target.responseText);
}
};
var fd=new FormData();
fd.append("that_random_filename.wav",audioBlob);
xhr.open("POST","<url>",true);
xhr.send(fd);
}
Then that method will save to server from inside the worker thread, rather than pushing it back to the main thread. (The complex Worker-based mechanism in RecorderJS is because a large encode should be done off-thread.)
Really, ideally, you'd just use a MediaRecorder today, and let it do the encoding, but that's a whole 'nother ball of wax.
I currently have javascript code (please see below) that searches an array for a month/day combination, and if it is found, assigns the name of a .jpg file (which is used for the background image of a page). Instead of hard-coding all of the data in the array, I'd like to be able to create an external .txt file with month/day codes and associated image file names, that could be read and loaded into the array. Thanks for your help!
var ourdates = ['0000','0118','0215','0530','0614','0704','0911','1111','1207']
if (ourdates.indexOf(monthday) != -1)
{
ourimage = "flag";
}
If you mean loading it from your server, that's a classic use-case for ajax, frequently combined with JSON:
var ourdates = null;
var xhr = new XMLHttpRequest();
xhr.open("GET", "/path/to/your/data");
xhr.onreadystatechange = function() {
if (xhr.readyState == 4 && xhr.status == 200) {
ourdates = JSON.parse(xhr.responseText);
// call something that uses `ourdates`
}
};
xhr.send(null)
If you mean from the user's computer, my answer here shows how to do that with the File API. Doing that requires an <input type="file"> input (or drag-and-drop event) that the user uses to grant access to the file to your script. You can't read a file from their machine without them specifically giving you access to the file.
I have an angularjs project which retrieves JSON files from a server and uses the contents to display the data in the screen.
I'm using a service to load the data, and this service calls the server for a new JSON file every 2 seconds (I removed that from the code below for simplicity).
var data = $resource(:file.json', {}, {
query: {method: 'GET', params: {file: '#file'}}
});
this.load = function(file, myFunction) {
data.query({file:file}, function(data) {
myFunction(data);
}
}
Now, these files can be really big and sometimes there's no need to process the file because there are no changes from the previous one received. I have a property in the JSON file with the version number, and I should not process the file unless that version number is higher than the one in the previous file.
I can do that by calling the query service, which loads the file contents into a js object and then check the version, if the file is really big it might take a while to load it. Is there a way to access that property value (version) ONLY and then, depending on it, load the file into a js object?
EDIT: The thing that I'm guessing is that loading a 1MB JSON file to check a version number inside it might take a while (or maybe no and that $resource action is really fast, anyone knows?), but I'm not really sure that it can be done any other way, as I'm checking a specific property inside the file.
Many thanks in advance.
HTML5 and Javascript now provides a File API which can be used to read the file line by line. You can find information regarding this feature here:
http://www.html5rocks.com/en/tutorials/file/dndfiles/
This will slice the full file into string and take just the first line(asuming the version is in there)
data.substr(0, data.indexOf("\n"));
--
Bonus:
Also in this answer you will find out how to read the first line of a file:
https://stackoverflow.com/a/12227851/2552259
var XHR = new XMLHttpRequest();
XHR.open("GET", "http://hunpony.hu/today/changelog-en.txt", true);
XHR.send();
XHR.onload = function (){
console.log( XHR.responseText.slice(0, XHR.responseText.indexOf("\n")) );
};
Another question with the same topic:
https://stackoverflow.com/a/6861246/2552259
var txtFile = new XMLHttpRequest();
txtFile.open("GET", "http://website.com/file.txt", true);
txtFile.onreadystatechange = function()
{
if (txtFile.readyState === 4) { // document is ready to parse.
if (txtFile.status === 200) { // file is found
allText = txtFile.responseText;
lines = txtFile.responseText.split("\n");
}
}
}
txtFile.send(null);
Do you have access to the json files?
I'm not sure how you generate your json files but you could try adding the version number in the filename and check if a newer filename exists. I have not tested this but maybe it's worth a try.
I'm trying to make a Chrome app that will have some animated objects in it.
I can load textures by using: new Image() and then setting the image's src property to the name of a file in my app's root directory. (This will load the texture)
Is it possible to do a similar thing for binary files that contain my proprietary animation data? I've looked and looked but I don't seem to find anything that lets me load a binary file that has NOT been picked by the user or dragged and dropped by the user.
If this is something that is not allowed, (presumably for security issues) anyone got any clever workarounds?
For files inside the app's package, it should be as simple as loading the file with XHR.
Use the fully-qualified URL to be on the safe side, obtained with chrome.runtime.getURL(pathRelativeToRoot)
This was what worked for me:
function reqError() {
console.log("Got an error");
}
function reqListener() {
var buffer = this.response;
console.log("Load complete! Length = ", buffer.byteLength);
}
function LoadBinaryFile(fileName) {
var path = chrome.runtime.getURL(fileName);
var oReq = new XMLHttpRequest();
oReq.onload = reqListener;
oReq.onerror = reqError;
oReq.open("GET", path, true);
oReq.responseType = "arraybuffer";
oReq.send();
}
I'm working on a testing framework that needs to pass files to the drop listener of a PLUpload instance. I need to create blob objects to pass inside a Data Transfer Object of the sort generated on a Drag / Drop event. I have it working fine for text files and image files. I would like to add support for PDF's, but it seems that I can't get the encoding right after retrieving the response. The response is coming back as text because I'm using Sahi to retrieve it in order to avoid Cross-Domain issues.
In short: the string I'm receiving is UTF-8 encoded and therefore the content looks like you opened a PDF with a text editor. I am wondering how to convert this back into the necessary format to create a blob, so that after the document gets uploaded everything looks okay.
What steps do I need to go through to convert the UTF-8 string into the proper blob object? (Yes, I am aware I could submit an XHR request and change the responseType property and (maybe) get closer, however due to complications with the way Sahi operates I'm not going to explain here why I would prefer not to go this route).
Also, I'm not familiar enough but I have a hunch maybe I lose data by retrieving it as a string? If that's the case I'll find another approach.
The existing code and the most recent approach I have tried is here:
var data = '%PDF-1.7%����115 0 obj<</Linearized 1/L ...'
var arr = [];
var utf8 = unescape(encodeURIComponent(data));
for (var i = 0; i < utf8.length; i++) {
arr.push(utf8.charCodeAt(i));
}
var file = new Blob(arr, {type: 'application/pdf'});
It looks like you were close. I just did this for a site which needed to read a PDF from another website and drop it into a fileuploader plugin. Here is what worked for me:
var url = "http://some-websites.com/Pdf/";
//You may not need this part if you have the PDF data locally already
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function () {
if (this.readyState == 4 && this.status == 200) {
//console.log(this.response, typeof this.response);
//now convert your Blob from the response into a File and give it a name
var fileOfBlob = new File([this.response], 'your_file.pdf');
// Now do something with the File
// for filuploader (blueimp), just use the add method
$('#fileupload').fileupload('add', {
files: [ fileOfBlob ],
fileInput: $(this)
});
}
}
xhr.open('GET', url);
xhr.responseType = 'blob';
xhr.send();
I found help on the XHR as blob here. Then this SO answer helped me with naming the File. You might be able to use the Blob by itself, but you won't be able to give it a name unless its passed into a File.