I need to get execution time in milliseconds.
I originally asked this question back in 2008. The accepted answer then was to use new Date().getTime() However, we can all agree now that using the standard performance.now() API is more appropriate. I am therefore changing the accepted answer to this one.
Using performance.now():
var startTime = performance.now()
doSomething() // <---- measured code goes between startTime and endTime
var endTime = performance.now()
console.log(`Call to doSomething took ${endTime - startTime} milliseconds`)
In Node.js it is required to import the performance class
importing performance
const { performance } = require('perf_hooks');
Using console.time: (living standard)
console.time('doSomething')
doSomething() // <---- The function you're measuring time for
console.timeEnd('doSomething')
Note: The string being passed to the time() and timeEnd() methods must match(for the timer to finish as expected).
console.time() documentations:
MDN documentation
Node.js documentation
use new Date().getTime()
The getTime() method returns the number of milliseconds since midnight of January 1, 1970.
ex.
var start = new Date().getTime();
for (i = 0; i < 50000; ++i) {
// do something
}
var end = new Date().getTime();
var time = end - start;
alert('Execution time: ' + time);
Don't use Date(). Read below.
Use performance.now():
<script>
var a = performance.now();
alert('do something...');
var b = performance.now();
alert('It took ' + (b - a) + ' ms.');
</script>
It works on:
IE 10 ++
FireFox 15 ++
Chrome 24 ++
Safari 8 ++
Opera 15 ++
Android 4.4 ++
etc, etc
console.time may be viable for you, but it's non-standard §:
This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
Besides browser support, performance.now seems to have the potential to provide more accurate timings as it appears to be the bare-bones version of console.time.
<rant> Also, DON'T EVER use Date for anything because it's affected by changes in "system time". Which means we will get invalid results —like "negative timing"— when the user doesn't have an accurate system time:
On Oct 2014, my system clock went haywire and guess what.... I opened Gmail and saw all of my day's emails "sent 0 minutes ago". And I'd thought Gmail is supposed to be built by world-class engineers from Google.......
(Set your system clock to one year ago and go to Gmail so we can all have a good laugh. Perhaps someday we will have a Hall of Shame for JS Date.)
Google Spreadsheet's now() function also suffers from this problem.
The only time you'll be using Date is when you want to show the user his system clock time. Not when you want to get the time or to measure anything.
If you need to get function execution time on your local development machine, you can either use your browser's profiling tools, or console commands such as console.time() and console.timeEnd().
All modern browsers have JavaScript profilers built-in. These profilers should give the most accurate measurement as you do not have to modify your existing code, which could affect the function's execution time.
To profile your JavaScript:
In Chrome, press F12 and select the Profiles tab, then Collect JavaScript CPU Profile.
In Firefox, install/open Firebug, and click on the Profile button.
In IE 9+, press F12, click on Script or Profiler (depending on your version of IE).
Alternatively, on your development machine, you can add instrumentation to your code with console.time() and console.timeEnd(). These functions, supported in Firefox11+, Chrome2+ and IE11+, report on timers that you start/stop via console.time(). time() takes a user-defined timer name as an argument, and timeEnd() then reports on the execution time since the timer started:
function a() {
console.time("mytimer");
... do stuff ...
var dur = console.timeEnd("myTimer"); // NOTE: dur only works in FF
}
Note that only Firefox returns the elapsed time in the timeEnd() call. The other browsers simply report the result to the developer console: the return value of timeEnd() is undefined.
If you want to get function execution time in the wild, you will have to instrument your code. You have a couple options. You can simply save the start and end times by querying new Date().getTime():
function a() {
var start = new Date().getTime();
... do stuff ...
var end = new Date().getTime();
var dur = end - start;
}
However, the Date object only has millisecond resolution and will be affected by any OS's system clock changes. In modern browsers, there's a better option.
The better option is to use the High Resolution Time, aka window.performance.now(). now() is better than the traditional Date.getTime() in two important ways:
now() is a double with submillisecond resolution that represents the number of milliseconds since the start of the page's navigation. It returns the number of microseconds in the fractional (e.g. a value of 1000.123 is 1 second and 123 microseconds).
now() is monotonically increasing. This is important as Date.getTime() can possibly jump forward or even backward on subsequent calls. Notably, if the OS's system time is updated (e.g. atomic clock synchronization), Date.getTime() is also updated. now() is guaranteed to always be monotonically increasing, so it is not affected by the OS's system time -- it will always be wall-clock time (assuming your wall clock is not atomic...).
now() can be used in almost every place that new Date().getTime(), + new Date andt Date.now() are. The exception is that Date and now() times don't mix, as Date is based on unix-epoch (the number of milliseconds since 1970), while now() is the number of milliseconds since your page navigation started (so it will be much smaller than Date).
Here's an example of how to use now():
function a() {
var start = window.performance.now();
... do stuff ...
var end = window.performance.now();
var dur = end - start;
}
now() is supported in Chrome stable, Firefox 15+, and IE10. There are also several polyfills available.
One other option for measuring execution time in the wild is UserTiming. UserTiming behaves similarly to console.time() and console.timeEnd(), but it utilizes the same High Resolution Timestamp that now() uses (so you get a sub-millisecond monotonically increasing clock), and saves the timestamps and durations to the PerformanceTimeline.
UserTiming has the concepts of marks (timestamps) and measures (durations). You can define as many of either as you want, and they're exposed on the PerformanceTimeline.
To save a timestamp, you call mark(startMarkName). To get the duration since your first mark, you simply call measure(measurename, startMarkname). The duration is then saved in the PerformanceTimeline alongside your marks.
function a() {
window.performance.mark("start");
... do stuff ...
window.performance.measure("myfunctionduration", "start");
}
// duration is window.performance.getEntriesByName("myfunctionduration", "measure")[0];
UserTiming is available in IE10+ and Chrome25+. There is also a polyfill available (which I wrote).
To get precise values you should use Performance interface. It's supported in modern versions of Firefox, Chrome, Opera and IE. Here's an example of how it can be used:
var performance = window.performance;
var t0 = performance.now();
doWork();
var t1 = performance.now();
console.log("Call to doWork took " + (t1 - t0) + " milliseconds.")
Date.getTime() or console.time() are not good for measuring precise execution time. You can use them if quick rough estimate is OK for you. By rough estimate I mean you can get 15-60 ms shift from the real time.
Check this brilliant post on measuring execution time in JavaScript. The author also gives a couple of links about accuracy of JavaScript time, worth reading.
Use Firebug, enable both Console and Javascript. Click Profile. Reload. Click Profile again. View the report.
A simple solution, you can use add operator also here
var start = +new Date();
callYourFunctionHere();
var end = +new Date();
var time = end - start;
console.log('total execution time = '+ time + 'ms');
process.hrtime() is available within Node.js - it returns a value in nanoseconds
let hrTime = process.hrtime()
console.log(hrTime[0] * 1000000 + hrTime[1] / 1000)
Here's a decorator for timing functions
It wraps functions so that they get timed each time they get run
Usage:
let test = () => { /* does something */ }
test = timed(test) // turns the function into a timed function in one line
test() // run your code as normal, logs 'function test took 1001.900ms'
This is the decorator:
let timed = (f) => (...args) => {
let start = performance.now();
let ret = f(...args);
console.log(`function ${f.name} took ${(performance.now() - start).toFixed(3)}ms`);
return ret;
}
If you're using async functions you can make timed async and add an await before f(...args), and that should work for those. It gets more complicated if you want one decorator to handle both sync and async functions.
var StopWatch = function (performance) {
this.startTime = 0;
this.stopTime = 0;
this.running = false;
this.performance = performance === false ? false : !!window.performance;
};
StopWatch.prototype.currentTime = function () {
return this.performance ? window.performance.now() : new Date().getTime();
};
StopWatch.prototype.start = function () {
this.startTime = this.currentTime();
this.running = true;
};
StopWatch.prototype.stop = function () {
this.stopTime = this.currentTime();
this.running = false;
};
StopWatch.prototype.getElapsedMilliseconds = function () {
if (this.running) {
this.stopTime = this.currentTime();
}
return this.stopTime - this.startTime;
};
StopWatch.prototype.getElapsedSeconds = function () {
return this.getElapsedMilliseconds() / 1000;
};
StopWatch.prototype.printElapsed = function (name) {
var currentName = name || 'Elapsed:';
console.log(currentName, '[' + this.getElapsedMilliseconds() + 'ms]', '[' + this.getElapsedSeconds() + 's]');
};
Benchmark
var stopwatch = new StopWatch();
stopwatch.start();
for (var index = 0; index < 100; index++) {
stopwatch.printElapsed('Instance[' + index + ']');
}
stopwatch.stop();
stopwatch.printElapsed();
Output
Instance[0] [0ms] [0s]
Instance[1] [2.999999967869371ms] [0.002999999967869371s]
Instance[2] [2.999999967869371ms] [0.002999999967869371s]
/* ... */
Instance[99] [10.999999998603016ms] [0.010999999998603016s]
Elapsed: [10.999999998603016ms] [0.010999999998603016s]
performance.now() is optional - just pass false into StopWatch constructor function.
It is possible to use only one variable:
var timer = -performance.now();
// Do something
timer += performance.now();
console.log("Time: " + (timer/1000).toFixed(5) + " sec.")
timer/1000 - to convert milliseconds to seconds
.toFixed(5) - to trim extra digits
To extend vsync's code further to have the ability to return the timeEnd as a value in NodeJS use this little piece of code.
console.timeEndValue = function(label) { // Add console.timeEndValue, to add a return value
var time = this._times[label];
if (!time) {
throw new Error('No such label: ' + label);
}
var duration = Date.now() - time;
return duration;
};
Now use the code like so:
console.time('someFunction timer');
someFunction();
var executionTime = console.timeEndValue('someFunction timer');
console.log("The execution time is " + executionTime);
This gives you more possibilities. You can store the execution time to be used for more purposes like using it in equations, or stored in a database, sent to a remote client over websockets, served on a webpage, etc.
there are multiple ways to achieve this objective :
using console.time
console.time('function');
//run the function in between these two lines for that you need to
//measure time taken by the function. ("ex. function();")
console.timeEnd('function');
this is the most efficient way :
using performance.now(), e.g.
var v1 = performance.now();
//run the function here for which you have top measure the time
var v2 = performance.now();
console.log("total time taken = "+(v2-v1)+"milliseconds");
use +(add operator) or getTime()
var h2 = +new Date(); //or
var h2 = new Date().getTime();
for(i=0;i<500;i++) { /* do something */}
var h3 = +new Date(); //or
var h3 = new Date().getTime();
var timeTaken = h3-h2;
console.log("time ====", timeTaken);
Here's what happens when you apply the unary plus operator to a Date instance:
Get the value of the Date instance in question
Convert it to a Number
NOTE: getTime() gives better performance than unary + operator.
It may help you.
var t0 = date.now();
doSomething();
var t1 = date.now();
console.log("Call to doSomething took approximate" + (t1 - t0)/1000 + " seconds.")
This is a Timer function. If you want to measure the time between multiple things that aren't nested:
function timer(lap){
if(lap) console.log(`${lap} in: ${(performance.now()-timer.prev).toFixed(3)}ms`);
timer.prev = performance.now();
}
Similar to console.time(), but easier usage if you don't need to keep track of previous timers.
Usage:
timer() // set the start
// do something
timer('built') // logs 'built in: 591.815ms'
// do something
timer('copied') // logs 'copied in: 0.065ms'
// do something
timer('compared') // logs 'compared in: 36.41ms'
If you like the blue color from console.time(), you can use this line instead
console.log(`${lap} in: %c${(performance.now()-timer.prev).toFixed(3)}ms`, 'color:blue');
Since console.time and performance.now aren't supported in some major browsers (i.e. IE10), I created a slim utility that utilizes the best available methods. However, it lacks error handling for false usages (calling End() on a not initialized timer).
Use it and improve it as you want.
Performance: {
Timer: {},
Start: function (name) {
if (console && console.time) {
console.time(name);
} else if (window.performance.now) {
this.Timer[name] = window.performance.now();
} else {
this.Timer[name] = new Date().getTime();
}
},
End: function (name) {
if (console && console.time) {
console.timeEnd(name);
} else {
var result;
if (window.performance.now) {
result = window.performance.now() - this.Timer[name];
} else {
result = new Date().getTime() - this.Timer[name];
}
console.log(name + ": " + result);
}
}
}
Use this code format
const startTime =new Date().getTime();
//do something
const endTime = new Date().getTime();
console.log(`time taken ${(endTime - startTime)/1000} seconds`);
A couple months ago I put together my own routine that times a function using Date.now() -- even though at the time the accepted method seemed to be performance.now() --
because the performance object is not yet available (built-in) in the stable Node.js release.
Today I was doing some more research and found another method for timing. Since I also found how to use this in Node.js code, I thought I would share it here.
The following is combined from the examples given by w3c and Node.js:
function functionTimer() {
performance.mark('start')
functionToBeTimed()
performance.mark('end')
performance.measure('Start to End', 'start', 'end')
const measure = performance.getEntriesByName('Start to End')[0]
console.log(measure.duration)
}
NOTE:
If you intend to use the performance object in a Node.js app, you must include the following require:
const { performance } = require('perf_hooks')
Thanks, Achim Koellner, will expand your answer a bit:
var t0 = process.hrtime();
//Start of code to measure
//End of code
var timeInMilliseconds = process.hrtime(t0)[1]/1000000; // dividing by 1000000 gives milliseconds from nanoseconds
Please, note, that you shouldn't do anything apart from what you want to measure (for example, console.log will also take time to execute and will affect performance tests).
Note, that in order by measure asynchronous functions execution time, you should insert var timeInMilliseconds = process.hrtime(t0)[1]/1000000; inside the callback. For example,
var t0 = process.hrtime();
someAsyncFunction(function(err, results) {
var timeInMilliseconds = process.hrtime(t0)[1]/1000000;
});
With performance
NodeJs: It is required to import the performance class
var time0 = performance.now(); // Store the time at this point into time0
yourFunction(); // The function you're measuring time for
var time1 = performance.now(); // Store the time at this point into time1
console.log("youFunction took " + (time1 - time0) + " milliseconds to execute");
Using console.time
console.time('someFunction');
someFunction(); // Whatever is timed goes between the two "console.time"
console.timeEnd('someFunction');
Use console.time('some label here') before the function and console.timeEnd('some label here') after the function. It will give you the running time of the function.
Stopwatch with cumulative cycles
Works with server and client (Node or DOM), uses the Performance API.
Good when you have many small cycles e.g. in a function called 1000 times that processes 1000 data objects but you want to see how each operation in this function adds up to the total.
So this one uses a module global (singleton) timer. Same as a class singleton pattern, just a bit simpler to use, but you need to put this in a separate e.g. stopwatch.js file.
const perf = typeof performance !== "undefined" ? performance : require('perf_hooks').performance;
const DIGITS = 2;
let _timers = {};
const _log = (label, delta?) => {
if (_timers[label]) {
console.log(`${label}: ` + (delta ? `${delta.toFixed(DIGITS)} ms last, ` : '') +
`${_timers[label].total.toFixed(DIGITS)} ms total, ${_timers[label].cycles} cycles`);
}
};
export const Stopwatch = {
start(label) {
const now = perf.now();
if (_timers[label]) {
if (!_timers[label].started) {
_timers[label].started = now;
}
} else {
_timers[label] = {
started: now,
total: 0,
cycles: 0
};
}
},
/** Returns total elapsed milliseconds, or null if stopwatch doesn't exist. */
stop(label, log = false) {
const now = perf.now();
if (_timers[label]) {
let delta;
if(_timers[label].started) {
delta = now - _timers[label].started;
_timers[label].started = null;
_timers[label].total += delta;
_timers[label].cycles++;
}
log && _log(label, delta);
return _timers[label].total;
} else {
return null;
}
},
/** Logs total time */
log: _log,
delete(label) {
delete _timers[label];
}
};
The best way would be to use the performance hooks module. Although unstable, you can mark specific areas of your code and measure the duration between marked areas.
const { performance, PerformanceObserver } = require('perf_hooks');
const measures = []
const obs = new PerformanceObserver(list => measures.push(...list.getEntries()));
obs.observe({ entryTypes: ['measure'] });
const getEntriesByType = cb => cb(measures);
const doSomething = val => {
performance.mark('beginning of the process');
val *= 2;
performance.mark('after multiplication');
performance.measure('time taken', 'beginning of the process', 'after multiplication');
getEntriesByType(entries => {
entries.forEach(entry => console.log(entry));
})
return val;
}
doSomething(4);
Try here
export default class Singleton {
static myInstance: Singleton = null;
_timers: any = {};
/**
* #returns {Singleton}
*/
static getInstance() {
if (Singleton.myInstance == null) {
Singleton.myInstance = new Singleton();
}
return this.myInstance;
}
initTime(label: string) {
this._timers[label] = Date.now();
return this._timers[label];
}
endTime(label: string) {
const endTime = Date.now();
if (this._timers[label]) {
const delta = endTime - this._timers[label];
const finalTime = `${label}: ${delta}ms`;
delete this._timers[label];
return finalTime;
} else {
return null;
}
}
}
InitTime related to string.
return Singleton.getInstance().initTime(label); // Returns the time init
return Singleton.getInstance().endTime(label); // Returns the total time between init and end
In my case, I perfer to use # grammar suger and compile it with babel.
The problem of this method is that function has to be inside object.
Sample JS Code
function timer() {
return (target, propertyKey, descriptor) => {
const start = Date.now();
let oldFunc = descriptor.value;
descriptor.value = async function (){
var result = await oldFunc.apply(this, arguments);
console.log(Date.now() - start);
return result;
}
}
}
// Util function
function delay(timeout) {
return new Promise((resolve) => setTimeout(() => {
resolve();
}, timeout));
}
class Test {
#timer()
async test(timout) {
await delay(timout)
console.log("delay 1");
await delay(timout)
console.log("delay 2");
}
}
const t = new Test();
t.test(1000)
t.test(100)
.babelrc (for babel 6)
{
"plugins": [
"transform-decorators-legacy"
]
}
To start the timer use console.time("myTimer");
Optional: To print the elapsed time, use
console.timeLog("myTimer");
Finally, to stop the timer and print the final
time: console.timeEnd("myTimer");
You can read more about this on MDN and in the Node.js documentation.
Available on Chrome, Firefox, Opera and NodeJS. (not on Edge or Internet Explorer).
Note: Simplest implementation of pure functional, ES6 method, no extra variables needed, just 3 lines of codes. Handles sync and async codes, so no external libraries needed, works in both JavaScript and Node JS, can even use to test the latency of your APIs
// Create one-liner timer function
let [timer, timingMonitor] = [0, () => timer = !timer ? Date.now() : `${Date.now() - timer}ms`]
// Initiate timer
timingMonitor();
// Your code here
doSomething();
// End timer
console.log(timingMonitor());
// Console output: "102ms", for example
Basic TypeScript example that supports marks. Calling start('something') will begin the timer and stop('something') will end the timer and return a formatted string containing elapsed time.
View Flems Example
/**
* Mark entries
*/
export const marks: { [id: string]: number } = {};
/**
* Start timing
*/
export const start = (id: string) => {
return Object.assign(marks, {[id]: Date.now() })[id]
}
/**
* Clear all
*/
export const clear = () => {
for (const id in marks) delete marks[id];
};
/**
* Stop timing and return formatted elapsed time
*/
export const stop = (id: string) => {
const ms = Date.now() - marks[id];
delete marks[id];
return ms > 1000
? `${(ms / 1000).toFixed(0)}s ${+ms.toFixed(0).slice(1)}ms`
: `${ms.toFixed(0)}ms`;
};
The example code is exporting each function. You can drop this into a project and call the methods accordingly from a default as import, eg:
import * as time from './timer.js'
time.start('foo')
// do something
console.log('elapsed time: ' + time.stop('bar'))
As previously stated check for and use built in timer. But if you want or need to write your own here is my two cents:
//=-=|Source|=-=//
/**
* JavaScript Timer Object
*
* var now=timer['elapsed']();
* timer['stop']();
* timer['start']();
* timer['reset']();
*
* #expose
* #method timer
* #return {number}
*/
timer=function(){
var a=Date.now();
b=0;
return{
/** #expose */
elapsed:function(){return b=Date.now()-a},
start:function(){return a=Date.now()},
stop:function(){return Date.now()},
reset:function(){return a=0}
}
}();
//=-=|Google Advanced Optimized|=-=//
timer=function(){var a=Date.now();b=0;return{a:function(){return b=Date.now()-a},start:function(){return a=Date.now()},stop:function(){return Date.now()},reset:function(){return a=0}}}();
Compilation was a success!
Original Size: 219 bytes gzipped (405 bytes uncompressed)
Compiled Size: 109 bytes gzipped (187 bytes uncompressed)
Saved 50.23% off the gzipped size (53.83% without gzip
The accepted answer is wrong !
Since JavaScript is asynchronous, the values of the variable end of the accepted answer would be wrong.
var start = new Date().getTime();
for (i = 0; i < 50000; ++i) {
// JavaScript is not waiting until the for is finished !!
}
var end = new Date().getTime();
var time = end - start;
alert('Execution time: ' + time);
The execution of the for may be very fast so you can not see that the result is wrong. You can test it with a code doing some request :
var start = new Date().getTime();
for (i = 0; i < 50000; ++i) {
$.ajax({
url: 'www.oneOfYourWebsites.com',
success: function(){
console.log("success");
}
});
}
var end = new Date().getTime();
var time = end - start;
alert('Execution time: ' + time);
So the alert will prompt very quickly but in the console you'll see that the ajax requests are continuing.
Here is how you should do it : https://developer.mozilla.org/en-US/docs/Web/API/Performance.now
I'm am doing a heavy "scientific" (ie, not displaying data) webgl computation. Webgl can't be put in a worker, and doing a lot of webgl blocks the whole browser so I sliced my computation in chunks, and I compute each chunk in a setTimeout() function (after calling getError() to flush the opengl queue). I leave a bit of time in between the chunks so that the browser has time to flush some UI events from the main UI queue and it makes the whole thing feel a bit less sluggish.
My problem is that when the tab is hidden, the setTimeout gets throttled to a one second period which is way too slow for me.
Is there a better solution than what I did? Obviously requestAnimationFrame() doesn't work, since it's never called back in hidden tabs (and it's too slow in visible).
Is there a non-throttled time event in the hidden state? I tried to use window.postMessage() but it's still too fast and the whole browser feels slow.
here is the current state of my research:
function drawTile(sequenceIndex) {
if (sequenceIndex < sequence.length) {
var x = sequence[sequenceIndex][0];
var y = sequence[sequenceIndex][1];
setTilePos(x, y);
modelStage.render(renderer, modelBuffer);
minkowskiPass.render(renderer, minkowskiBuffer, modelBuffer);
copyPass.quad.position.x = x;
copyPass.quad.position.y = y;
copyPass.render(renderer, null, minkowskiBuffer);
var gl = renderer.getContext();
gl.getError();
sequenceIndex++;
if (document.visibilityState != "hidden") {
setTimeout(function () {
drawTile(sequenceIndex);
}, 10);
} else {
//window.postMessage is not rate limited then the tab is hidden
// we need to slow the computation by an event, otherwise the whole browser is unresponsive.
$(window).one('message', function () {
drawTile(sequenceIndex);
});
window.postMessage('lol', '*');
}
} else
console.timeEnd('computation');
}
console.time('computation');
drawTile(0);
Here's another convoluted workaround for anyone who needs it; you can use the Web Audio API to generate function calls:
var setTimeout2 = (function () {
var samples = 2048;
var fns = [];
var context = new AudioContext();
var source = context.createBufferSource();
var node = context.createScriptProcessor(samples, 1, 1);
// This gets fired every ~46 milliseconds. You can change
// `samples` to another valid value (256, 512, 1024, 2048,
// 4096, 8192, or 16384); then it'll get called every
// `samples / context.sampleRate` seconds (~46 ms for
// `samples == 2048` and `context.sampleRate == 44100`).
node.onaudioprocess = function (e) {
fns = fns.filter(function (fn) {
return !fn(Date.now() - fn.t);
});
};
source.connect(node);
node.connect(context.destination);
window.do_not_garbage_collect = [context, source, node];
return function (fn) {
fn.t = Date.now();
fns.push(fn);
};
}());
// Use like this:
setTimeout2(function (t) {
console.log(t);
// End after 1 second.
if (t > 1000)
return true;
})
Perhaps have a worker thread also run a
postMessage loop and a fraction of the time (every n iterations), either pause or resume the main thread?
I've been trying to recreate a countdown timer similar to the one gmail uses that when you get disconnected from internet. The ajax request fails then it begin a short countdown then makes another ajax request and if it fails again then begin a longer countdown and so forth. Once a determined countdown value is reached (lets say 1 minute), the countdown is maintained at 1 minute until the internet connection is recovered or the servers comes back.
I don't want to use a plugin because this code will be embedded in a micro-controller that has limited space and also prefer not to place it as external file for practical reasons, even though jQuery library will already be external.
Everything should trigger onload, and continue automatically (i.e. no control inputs will be used).
So far I've developed code that does what I want if the ajax request succeeds or fails immediately but if there is a latency on the ajax request status (as for example having the server down) the browser won't produce an immediate result and my code fails.
I know what I stated above because I actually took the server down and was been help by firebug on Mozilla Firefox to see that the ajax result (success or failure) wasn't triggered immediately but keep waiting for several seconds.
Help please!
html code:
<div id='tempFail' ></div>
jQuery code:
$(document).ready(function()
{
//do when DOM ready - http://api.jquery.com/ready/
var timerSpeed = [1000, 5000, 10000, 20000, 30000, 60000];
// current time in ms since 1/1/1970, plus the initial reload interval
var end = (new Date).getTime() + timerSpeed[1];
var n=0;
var m=0;
setInterval(function()
{
var now = (new Date).getTime();
// Current time left to re-load in seconds, sometimes it goes to negative values, see below
var secLeft = Math.floor(( end - now ) / 1000);
// if secLeft is negative multiply by zero...equal to secLeft=0, this will produce an error of one second approximately
var timeToload = (secLeft < 0) ? secLeft * 0 : secLeft;
if (n!=0)
{
//check for failed or delayed request\n\
$('#tempFail').html('Failed or delayed response. Will auto load in: '+timeToload+ ' seconds!');
}
if( (secLeft)<=0)// if reload time is reached do
{
if (m==0)//used to prevent multiple continue reloads when ajax request status is not yet defined
{
m=1;
$.getScript('script_vars.js').done(function (data)
{
//if request succeeded
m=0;
n = 0;
end = (new Date).getTime() + timerSpeed[1];
// Time to load after the initial interval set above
$('#tempFail').html('');
//other code on success here
})
.fail(function()
{
//if request failed
m=0;
n ++;
if(n==6) n=5;
switch(n){ //timer delay for failed request\n\
case 1:
end = (new Date).getTime() + timerSpeed[1];
break;
case 2:
end = (new Date).getTime() + timerSpeed[2];
break;
case 3:
end = (new Date).getTime() + timerSpeed[3];
break;
case 4:
end = (new Date).getTime() + timerSpeed[4];
break;
case 5:
end = (new Date).getTime() + timerSpeed[5];
break;
}
});
}
}
}, 1000);
});
You asked for an example so I've written the following, you may want to wrap the contents of the function within another function so you can repeat it/don't have to worry about namespaces/etc. Didn't test so don't expect bug free!
Using window.setTimeout for every action, separated each stage into it's own function so code paths can more easily be followed.
$(document).ready(function () { // http://api.jquery.com/ready/
var $tempFail = $('#tempFail'),
delay = [1000, 5000, 10000, 20000, 30000, 60000],
delay_index = 0,
delay_ends = 0,
inform_user_ref = null,
inform_user = function inform_user() {
var now = (new Date).getTime(),
delta; // for difference, calculate later
if (delay_ends > now) { // if we're waiting for a retry
delta = Math.floor((delay_ends - now ) / 1000); // calculate time to wait
$tempFail.html('Failed or delayed response. Will auto load in: '+delta+ ' seconds!'); // let people know
window.setTimeout(inform_user, 200); // loop countdown timer
// can fast refresh this as it's just a countdown
}
},
get_success = function () {
$tempFail.html('');
// .. code on success
},
get_fail = function () {
delay_index < 5 && ++delay_index; // increment delay_index
get_initialise(); // retry
window.clearTimeout(inform_user_ref); // remove any old countdown timer
inform_user_ref = inform_user(); // and display new countdown
},
get_try = function () {
$.getScript('script_vars.js')
.done(get_success)
.fail(get_fail);
},
get_initialise = function () {
delay_ends = (new Date).getTime() + delay[delay_index];
window.setTimeout(get_try, delay[delay_index]); // retry
};
get_initialise(); // initial
});
Wow! Mr Paul S. your code was crazy good. I just made a couple of adjustments to have it perfectly working as I need it.
Added the following on ajax success:
delay_index = 0; //reset delay_index
get_initialise(); // retry
so I keep the code running every 5 seconds if everything goes ok.
2.
Added two new variables: let_cntDwn_end and ajax_rqst_status to avoid countdown number jumping (to let countdown finish before beginning the next one ) and to display a message while the ajax request haven't given any result respectively.
Here is the new code:
$(document).ready(function(){ //do when DOM ready - http://api.jquery.com/ready/
var $tempFail = $('#tempFail'),
delay = [5000, 5000, 10000, 20000, 30000, 60000],
delay_index = 0,
delay_ends = 0,
inform_user_ref = null,
let_cntDwn_end = 0,
ajax_rqst_status = 0, //ajax success or failure triggered
inform_user = function inform_user() {
var now = (new Date).getTime(),
delta; // for difference, calculated later
if (delay_ends > now) { // if we're waiting for a retry
let_cntDwn_end = 1;
delta = Math.floor((delay_ends - now ) / 1000); // calculate time to wait
if (ajax_rqst_status==0){
$tempFail.html('Failed response. Will auto load in: '+delta+ ' seconds!'); // let people know
window.setTimeout(inform_user, 900); // loop countdown timer
// can fast refresh this as it's just a countdown
}
}
else {let_cntDwn_end = 0; get_try();}
},
get_success = function () {
ajax_rqst_status =0;
$tempFail.html('');
// .. code on success
delay_index = 0; //reset delay_index
get_initialise(); // retry
},
get_fail = function () {
ajax_rqst_status =0;
delay_index < 5 && ++delay_index; // increment delay_index
get_initialise(); // retry
window.clearTimeout(inform_user_ref); // remove any old countdown timer
inform_user_ref = inform_user(); // and display new countdown
},
get_try = function () {
if (let_cntDwn_end == 0){
ajax_rqst_status=1;
$tempFail.html('Waiting for Ajax request success or failure'); // let people know
$.getScript('script_vars.js')
.done(get_success)
.fail(get_fail);
}
},
get_initialise = function () {
delay_ends = (new Date).getTime() + delay[delay_index];
window.setTimeout(get_try, delay[delay_index]); // retry
};
get_initialise(); // initial
});
There's also JS lib which handles this for you by monitoring ajax requests.
https://github.com/HubSpot/offline
I've built a simple JavaScript-based timer for a mobile webapp; for the sake of example:
var a = 0;
setInterval(function() {
console.log('a', a);
a++;
}, 1000);
This runs just fine in both Mobile Safari and Android Browser. It will log to console every second and increment the value of a accordingly. (Okay, Android Browser doesn't have console.log support, but let's assume it does.)
The issue: if the screen times out (i.e. user stopped interacting with the page), the setInterval function pauses. It resumes when the user turns on their screen again. This won't work for me as I need timer to keep running.
The questions: Is there a way to prevent the setInterval function from pausing when the screen times out? If not, is it possible to prevent the screen from timing out? Any other alternatives?
Thanks in advance!
Basically, no. The phone enters a sleep state to save battery when the screen times out. Since you can't see anything anyway, a large number of processing tasks are stopped. Similar things will occur when you change tabs/windows (the page is unloaded from memory). Right now there is no way to request that the device stays on from a web application. Future support in Android for accessing hardware may provide this functionality, but personally I doubt it.
If you need always running support, you'll need to write native applications for both systems (plus on Android it can always run).
You can use the Page Visibility API to detect when the page is hidden or visible. For example, if the user navigates away from the browser and back again or the screen turns off and on.
I used this answer to help create by solution.
You will need to store the time you set your interval. Then when the visibilityChange event listener indicates the document is visible again, you can calculate the amount of time that has passed since you first started the interval and update your data as needed.
In my case I was creating a count down timer in my Angular2 project. My page was running on an iPad and the timer was pausing whenever the screen turned off. So I added the event listener in my ngOnInit(). Then when the screen turned back on I could update my timer to show the correct time left since it was started.
I am using the moment npm package to handle my date time.
The timerInfo object is a class variable that gets updated by the interval callback. self.zone.run() is used to propagate the changes to the DOM so that the updated time gets displayed.
Written in typescript:
private timerInfo:{
days?:number,
hours?:number,
minutes:number,
seconds:number
};
private startTime:Moment = moment();
private timerDuration:number = 20; // in minutes
private timerHandle:any;
ngOnInit() {
this.setVisibilityListener();
}
private setVisibilityListener():void {
var self = this;
var hidden, visibilityState, visibilityChange;
if (typeof document.hidden !== "undefined") {
hidden = "hidden";
visibilityChange = "visibilitychange";
visibilityState = "visibilityState";
}
var document_hidden = document[hidden];
document.addEventListener(visibilityChange, function () {
if (document_hidden != document[hidden]) {
if (document[hidden]) {
// Document hidden
console.log("document hidden");
} else {
// Document shown
console.log("document shown; setCountDownTimer()");
self.setCountDownTimer();
}
document_hidden = document[hidden];
}
});
}
private setCountDownTimer():void {
var self = this;
if (self.startTime) {
var startMoment = moment(self.startTime);
var endMoment = startMoment.add(self.timerDuration, "minutes");
console.log("endMoment: ", endMoment.toISOString());
self.clearTimer();
var eventTime = endMoment.unix();
var currentTime = moment().unix();
var diffTime = eventTime - currentTime;
var duration = moment.duration(diffTime * 1000, 'milliseconds');
var interval = 1000;
// if time to countdown
if (diffTime > 0) {
self.timerHandle = setInterval(() => {
self.zone.run(() => {
var diff = duration.asMilliseconds() - interval;
if (diff < 0) {
self.clearTimer();
self.timerComplete();
} else {
duration = moment.duration(duration.asMilliseconds() - interval, 'milliseconds');
self.timerInfo = {
days: moment.duration(duration).days(),
hours: moment.duration(duration).hours(),
minutes: moment.duration(duration).minutes(),
seconds: moment.duration(duration).seconds()
};
// console.log("timerInfo: ", JSON.stringify(self.timerInfo));
}
});
}, 1000);
} else {
self.timerComplete();
}
}
}
private clearTimer():void {
if (this.timerHandle) {
clearInterval(this.timerHandle);
this.timerHandle = null;
}
}