Click and hold event in vanilla javascript - javascript

I'd like to be able to have a function attached to an element which will only run once a click has been held on that element for a given amount of time.
There are several (1, 2, 3) questions relating to handling mouse holds in javascript; but these questions either use jQuery or relate to a more particular use case.
I'd like to implement something more general, and I feel like there ought to be a good answer on stack overflow for this problem.

Here is what I get using window.setTimeout :
var mouseTimer;
var myVar;
function mouseDown() {
mouseTimer = window.setTimeout(myFunction,500); //set timeout to fire in 2 seconds when the user presses mouse button down
}
function myFunction(){ myVar = true;}
var div = document.getElementById("testBtn");
testBtn.addEventListener("mousedown", mouseDown);
document.body.addEventListener("mouseup", removeTimer);
function removeTimer(){
if(myVar) console.log("a");
if (mouseTimer) window.clearTimeout(mouseTimer);
myVar = false;
}
<button id="testBtn">Test</button>

function handleClickHold(el, timeout, callback) {
let startTime;
const mouseDown = () => (startTime = Date.now());
const mouseUp = (e) => Date.now() - startTime > timeout && callback(Date.now() - startTime);
el.addEventListener("mousedown", mouseDown);
el.addEventListener("mouseup", mouseUp);
}
const timeout = 500 // time in ms
const btn = document.querySelector('button');
const callback = (ms) => console.log('Held Button for ' + ms + ' ms')
handleClickHold(btn, timeout, callback);
<button>Click</button>
If you want something more general use, you could use a function like this. Takes an element, a timeout, and a callback, so you can apply it in different situations. You can pass the event to the callback as well.

Here's one way of doing it, though it feels rather verbose:
const addHoldListener = (element, f, timeout) => {
let down = 0;
let up = 0;
const upListener = () => {
up = Date.now();
const diff = up - down;
if (diff >= timeout) {
f();
}
element.removeEventListener('mouseup', upListener);
};
const downListener = () => {
down = Date.now();
element.addEventListener('mouseup', upListener);
};
element.addEventListener('mousedown', downListener);
};
addHoldListener(
document.querySelector('button'),
() => console.log('a'),
500
)
<button>Test</button>

Related

Javascript variable reference and/or copy

i have e video that i am scrolling with my mousewheel.
Everything is working fine but i would like to check if the user is still scrolling and if it is not so after 10 seconds i would like the video/scrollposition to set-back to zero.
The set-back is working but it is not happing after the "Interval". It is jumping back immediately.
This is my code so far:
const action = document.querySelector(".action");
const video = action.querySelector("video");
//Scroll Magic scenes
const controller = new ScrollMagic.Controller();
let scene = new ScrollMagic.Scene({
duration: 200000, //64000
triggerElement: action,
triggerHook: 0
})
.addIndicators()
.setPin(action)
.addTo(controller);
//Scroll Magic video animation
let accelAmount = 0.1;
let scrollpos = 0;
let currentTime = video.currentTime;
let lastcurrentTime;
let delay = 0;
scene.on("update", e => {
scrollpos = e.scrollPos / 3000; //the higher the number, the slower
});
//Move
setInterval(() => {
delay += (scrollpos - delay) * accelAmount;
video.currentTime = delay;
console.log(video.currentTime + " reading");
lastcurrentTime = video.currentTime;
}, 33.3);
//check if is still scrolling after x seconds
setInterval(checkTime, 10000);
//funktion to execute the check
function checkTime() {
console.log("waiting for new reading");
console.log(video.currentTime + " newreading");
currentTime = video.currentTime;
if (currentTime === lastcurrentTime) {
//is not scrolling -- go to start
//video.currentTime = 0;
window.scrollTo(0, 0);
}
}
You are updating the lastcurrentTime every 33.3ms and you're calling checkTime every 10s. So almost every time you call the checkTime, the lastcurrentTime will be synced with the video.currentTime.
I think that I would try something like this:
let setbackTimeout
scene.on("update", e => {
clearTimeout(setbackTimeout);
scrollpos = e.scrollPos / 3000; //the higher the number, the slower
setbackTimeout = setTimeout(checkTime, 10000);
});
every time you get an update you clear the countdown to setback and create another that you execute 10s later.
Listen to the scroll event listener. With a debounce-like function you can start a timeout that will run whenever the use stops scrolling.
The example below uses the aformentioned technique and shows a message whenever the user stops scrolling for 1 second.
function scrollTracker(delay, callback) {
let timeout = null;
return function(...args) {
if (timeout !== null) {
clearTimeout(timeout);
timeout = null;
}
timeout = setTimeout(callback, delay, ...args)
};
}
const tracker = scrollTracker(1000, () => {
console.log('User stopped scrolling. Handle your video here');
});
window.addEventListener('scroll', tracker);
#page {
height: 20000px;
}
<div id="page"></div>
I think your concept is wrong. I made a little demo how to implement it. It will print the message after 4 sec "inactivity" on button.
const btn = document.querySelector("button")
let myInterval = setInterval(myPrint, 4000)
btn.addEventListener("click", () => {
clearInterval(myInterval)
myInterval = setInterval(myPrint, 4000)
})
function myPrint(){
clearInterval(myInterval)
console.log("programming <3")
}
<button>Click me!</button>

function not working when i click button?

when i click my button, a timer is supposed to display a countdown timer. But the button does not work.
let timerCounter = document.getElementById("timer-counter");
let timer;
let timerCount;
function startTimer() {
timer = setInterval(function() {
timerCount--;
timerElement.textContent = "Time; " + timerCount;
if (timerCount === 0) {
clearInterval(timer);
}
});
}
startButton.addEventListener("click", startTimer);
This is what I found so far:
You are decrementing the timerCount, need to specify the initial value for it to work.
You're using timerElement instead of timerCounter that you've declared.
You must pass the second args to the setInterval which is delay.
const timerCounter = document.getElementById('timer-counter');
const startButton = document.getElementById('start-button');
let timer;
let timerCount = 30;
startButton.addEventListener('click', startTimer);
function startTimer() {
timer = setInterval(function () {
timerCount--;
timerCounter.textContent = 'Time; ' + timerCount;
if (timerCount === 0) {
clearInterval(timer);
}
}, 1000);
}
<div id="timer-counter"></div>
<button id="start-button">Start</button>
Here's a slightly different approach that avoids some of the problems with global variables. The function the listener calls initialises the count, and then returns a new function (a closure) that is called when the button is clicked. It also uses setTimeout which I find more easy to understand.
// Cache your elements
const counter = document.querySelector('#counter');
const startButton = document.querySelector('button');
// Initialise your count variable
function startTimer(count = 30) {
// Return a function that is called from
// the listener
return function loop () {
// Disabled the button once it's been clicked
if(!startButton.disabled) startButton.disabled = true;
counter.textContent = `Time: ${count}`;
if (count > 0) {
setTimeout(loop, 500, --count);
}
}
loop();
}
// Call startTimer to initialise the count, and return
// a new function that is used as the listener
startButton.addEventListener('click', startTimer(), false);
<div id="counter"></div>
<button>Start</button>
I'm sure this could be improved.
In this example we don't go below 0.
We don't allow timeout collisions ( timeouts don't stack causing weird counting speeds ).
We can reset to the original number when on 0.
const c = document.getElementById('timer-counter')
const b = document.getElementById('start-button')
let timer = false
let timerCount = 30
b.addEventListener('click', start)
function decrement() {
if(timerCount < 0) {
timerCount = 30
timer = false
return
}
c.innerText = `Count: ${timerCount}`
timerCount--
timer = setTimeout(decrement, 200)
}
function start() {
if(timer) return
decrement()
}
<div id="timer-counter"></div>
<button id="start-button">Start</button>

Element.scrollIntoView(); Not working in Chrome and Edge, Works in Firefox?

Let me preface by saying I am relatively green in respect to JavaScript. However, I am trying to create a JavaScript function that will listen for a wheel event, determine the direction of the scroll and scroll the next part of the page into view. Similar to a swipe gesture. I have it working in Firefox as intended, user scrolls down the page moves down, up the page moves up. However, in Chrome and Edge, the element.scrollIntoView() function seems to be called, but nothing happens.
I am using Blazor with JSInterop to get the page to scroll.
Here is the gist of the file:
// scrolldetection.js //
window.scrolldetection {
scrollSetup: function (elementId) {
autoscroller(elementId);
}
}
function autoscroller(elementId) {
// Set up vars
var idList = document.getElementById(elementId).children.id;
var idListIndex = // Gets current index based on current location on page
var curDirection;
document.addEventListener("wheel", function () {
var currentPos = window.scrollY;
if (!curDirection) {
// Check for what direction user scrolls
idListIndex = // Function that determines new index
scrollScreen(idList, idListIndex);
}
var timerId = setTimeout(function () {
curDirection = undefined;
clearTimeout(timerId);
}, 700);
}
}
function scrollScreen(idList, curIndex) {
console.log("list index: " + curIndex);
element = document.getElementById(idList[curIndex]);
console.log(element.id);
element.scrollIntoView({ behavior: 'smooth' });
}
I have another function that calls scrollIntoView() on the same elements, via a button press. Works just fine.
Here is that function:
// anchorlink.js // This one works as intended //
window.anchorlink = {
scrollIntoView: function (elementId) {
var elem = document.getElementById(elementId);
if (elem) {
elem.scrollIntoView({ behavior: 'smooth' });
}
}
}
The console.log() calls within the scrollScreen() function show up properly in the console in each browser. Leading me to believe that element.scrollIntoView() is being called, but something is going wrong to make it not function appropriately. If there is any other information you need, I will be happy to provide, thanks.
After working on this some more, I decided the concept I was using wasn't as user friendly as I had hoped.
I decided to let the user scroll freely along the page and when they stop scrolling, then determine the closest DOM element and scroll to it. Works on Edge, Chrome and Firefox.
window.contentcenter = {
contentCenter: function (elementId) {
var centeringFunction = debounce(function () { autocenter(elementId) }, 200);
document.addEventListener("scroll", centeringFunction);
}
}
function autocenter(elementId) {
var currentElement = detectCurrentElement(elementId);
currentElement.scrollIntoView({ behavior: "smooth" });
}
function detectCurrentElement(elementId) {
var element = document.getElementById(elementId);
var currentPos = window.scrollY;
var contentIdList = getContentIdList(elementId);
var currentElement = closestContent(currentPos, element, contentIdList);
return currentElement;
}
function closestContent(pos, element, contentIdList) {
var contentId = Math.round(pos / (element.offsetHeight / contentIdList.length));
var currentElement = document.getElementById(contentIdList[contentId]);
return currentElement;
}
function getContentIdList(elementId) {
var idList = []
var childElements = document.getElementById(elementId).children;
for (var i = 0; i < childElements.length; i++) {
idList.push(childElements[i].id);
}
return idList;
}
function debounce(func, timeout) {
var timer;
return function () {
var context = this, args = arguments;
var later = function () {
timer = null;
func.apply(context, args);
};
clearTimeout(timer);
timer = setTimeout(later, timeout)
};
}

How to implement the lodash _.throttle in vanilla javascript? [duplicate]

I am looking for a simple throttle in JavaScript. I know libraries like lodash and underscore have it, but only for one function it will be overkill to include any of those libraries.
I was also checking if jQuery has a similar function - could not find.
I have found one working throttle, and here is the code:
function throttle(fn, threshhold, scope) {
threshhold || (threshhold = 250);
var last,
deferTimer;
return function () {
var context = scope || this;
var now = +new Date,
args = arguments;
if (last && now < last + threshhold) {
// hold on to it
clearTimeout(deferTimer);
deferTimer = setTimeout(function () {
last = now;
fn.apply(context, args);
}, threshhold);
} else {
last = now;
fn.apply(context, args);
}
};
}
The problem with this is: it fires the function once more after the throttle time is complete. So let's assume I made a throttle that fires every 10 seconds on keypress - if I do keypress 2 times, it will still fire the second keypress when 10 seconds are completed. I do not want this behavior.
I would use the underscore.js or lodash source code to find a well tested version of this function.
Here is the slightly modified version of the underscore code to remove all references to underscore.js itself:
// Returns a function, that, when invoked, will only be triggered at most once
// during a given window of time. Normally, the throttled function will run
// as much as it can, without ever going more than once per `wait` duration;
// but if you'd like to disable the execution on the leading edge, pass
// `{leading: false}`. To disable execution on the trailing edge, ditto.
function throttle(func, wait, options) {
var context, args, result;
var timeout = null;
var previous = 0;
if (!options) options = {};
var later = function() {
previous = options.leading === false ? 0 : Date.now();
timeout = null;
result = func.apply(context, args);
if (!timeout) context = args = null;
};
return function() {
var now = Date.now();
if (!previous && options.leading === false) previous = now;
var remaining = wait - (now - previous);
context = this;
args = arguments;
if (remaining <= 0 || remaining > wait) {
if (timeout) {
clearTimeout(timeout);
timeout = null;
}
previous = now;
result = func.apply(context, args);
if (!timeout) context = args = null;
} else if (!timeout && options.trailing !== false) {
timeout = setTimeout(later, remaining);
}
return result;
};
};
Please note that this code can be simplified if you don't need all the options that underscore support.
Please find below a very simple and non-configurable version of this function:
function throttle (callback, limit) {
var waiting = false; // Initially, we're not waiting
return function () { // We return a throttled function
if (!waiting) { // If we're not waiting
callback.apply(this, arguments); // Execute users function
waiting = true; // Prevent future invocations
setTimeout(function () { // After a period of time
waiting = false; // And allow future invocations
}, limit);
}
}
}
Edit 1: Removed another reference to underscore, thx to #Zettam 's comment
Edit 2: Added suggestion about lodash and possible code simplification, thx to #lolzery #wowzery 's comment
Edit 3: Due to popular requests, I added a very simple, non-configurable version of the function, adapted from #vsync 's comment
What about this?
function throttle(func, timeFrame) {
var lastTime = 0;
return function () {
var now = Date.now();
if (now - lastTime >= timeFrame) {
func();
lastTime = now;
}
};
}
Simple.
You may be interested in having a look at the source.
callback: takes the function that should be called
limit: number of times that function should be called within the time limit
time: time span to reset the limit count
functionality and usage: Suppose you have an API that allows user to call it 10 times in 1 minute
function throttling(callback, limit, time) {
/// monitor the count
var calledCount = 0;
/// refresh the `calledCount` varialbe after the `time` has been passed
setInterval(function(){ calledCount = 0 }, time);
/// creating a closure that will be called
return function(){
/// checking the limit (if limit is exceeded then do not call the passed function
if (limit > calledCount) {
/// increase the count
calledCount++;
callback(); /// call the function
}
else console.log('not calling because the limit has exceeded');
};
}
////////////////////////////////////////////////////////////
// how to use
/// creating a function to pass in the throttling function
function cb(){
console.log("called");
}
/// calling the closure function in every 100 milliseconds
setInterval(throttling(cb, 3, 1000), 100);
Adding to the discussion here (and for more recent visitors), if the reason for not using the almost de facto throttle from lodash is to have a smaller sized package or bundle, then it's possible to include only throttle in your bundle instead of the entire lodash library. For example in ES6, it would be something like:
import throttle from 'lodash/throttle';
Also, there is a throttle only package from lodash called lodash.throttle which can be used with a simple import in ES6 or require in ES5.
I've just needed a throttle/debounce function for window resize event, and being curious, I also wanted to know what these are and how they work.
I've read multiple blog posts and QAs on SO, but they all seem to overcomplicate this, suggest libraries, or just provide descriptions and not simple plain JS implementations.
I won't provide a description since it's plentiful. So here's my implementation:
function throttle(callback, delay) {
var timeoutHandler = null;
return function () {
if (timeoutHandler == null) {
timeoutHandler = setTimeout(function () {
callback();
timeoutHandler = null;
}, delay);
}
}
}
function debounce(callback, delay) {
var timeoutHandler = null;
return function () {
clearTimeout(timeoutHandler);
timeoutHandler = setTimeout(function () {
callback();
}, delay);
}
}
These might need tweaks (e.g., initially the callback isn't called immediately).
See the difference in action (try resizing the window):
function throttle(callback, delay) {
var timeoutHandler = null;
return function () {
if (timeoutHandler == null) {
timeoutHandler = setTimeout(function () {
callback();
timeoutHandler = null;
}, delay);
}
}
}
function debounce(callback, delay) {
var timeoutHandler = null;
return function () {
clearTimeout(timeoutHandler);
timeoutHandler = setTimeout(function () {
callback();
}, delay);
}
}
var cellDefault = document.querySelector("#cellDefault div");
var cellThrottle = document.querySelector("#cellThrottle div");
var cellDebounce = document.querySelector("#cellDebounce div");
window.addEventListener("resize", function () {
var span = document.createElement("span");
span.innerText = window.innerWidth;
cellDefault.appendChild(span);
cellDefault.scrollTop = cellDefault.scrollHeight;
});
window.addEventListener("resize", throttle(function () {
var span = document.createElement("span");
span.innerText = window.innerWidth;
cellThrottle.appendChild(span);
cellThrottle.scrollTop = cellThrottle.scrollHeight;
}, 500));
window.addEventListener("resize", debounce(function () {
var span = document.createElement("span");
span.innerText = window.innerWidth;
cellDebounce.appendChild(span);
cellDebounce.scrollTop = cellDebounce.scrollHeight;
}, 500));
table {
border-collapse: collapse;
margin: 10px;
}
table td {
border: 1px solid silver;
padding: 5px;
}
table tr:last-child td div {
width: 60px;
height: 200px;
overflow: auto;
}
table tr:last-child td span {
display: block;
}
<table>
<tr>
<td>default</td>
<td>throttle</td>
<td>debounce</td>
</tr>
<tr>
<td id="cellDefault">
<div></div>
</td>
<td id="cellThrottle">
<div></div>
</td>
<td id="cellDebounce">
<div></div>
</td>
</tr>
</table>
JSFiddle
Here's how I implemented throttle function in ES6 in 9LOC, hope it helps
function throttle(func, delay) {
let timeout = null
return function(...args) {
if (!timeout) {
timeout = setTimeout(() => {
func.call(this, ...args)
timeout = null
}, delay)
}
}
}
Click on this link to see how it works.
I've seen a lot of answers here that are way too complex for "a simple throttle in js".
Almost all of the simpler answers just ignore calls made "in throttle" instead of delaying execution to the next interval.
Here's a simple implementation that also handles calls "in throttle":
const throttle = (func, limit) => {
let lastFunc;
let lastRan = Date.now() - (limit + 1); //enforces a negative value on first run
return function(...args) {
const context = this;
clearTimeout(lastFunc);
lastFunc = setTimeout(() => {
func.apply(context, args);
lastRan = Date.now();
}, limit - (Date.now() - lastRan)); //negative values execute immediately
}
}
This is almost the exact same implementation for a simple debounce. It just adds a calculation for the timeout delay which requires tracking when the function was last ran. See below:
const debounce = (func, limit) => {
let lastFunc;
return function(...args) {
const context = this;
clearTimeout(lastFunc);
lastFunc = setTimeout(() => {
func.apply(context, args)
}, limit); //no calc here, just use limit
}
}
Simple solution in ES6. Codepen Demo
const handleOnClick = () => {
console.log("hello")
}
const throttle = (func, delay) => {
let timeout = null;
return function (...args) {
if (timeout === null) {
func.apply(this, args);
timeout = setTimeout(() => {
timeout = null;
}, delay)
}
}
}
document.querySelector("#button").addEventListener("click", throttle(handleOnClick, 500))
<button type="button" id="button">Click me</button>
Here's my own version of Vikas post:
throttle: function (callback, limit, time) {
var calledCount = 0;
var timeout = null;
return function () {
if (limit > calledCount) {
calledCount++;
callback();
}
if (!timeout) {
timeout = setTimeout(function () {
calledCount = 0
timeout = null;
}, time);
}
};
}
I find that using setInterval is not a good idea.
With leading and trailing invocations:
const throttle = (fn, ms) => {
let locked = false
return function () {
if (!locked) {
locked = true
fn.apply(this, arguments)
setTimeout(() => {
fn.apply(this, arguments)
locked = false
}, ms)
}
}
}
Test case:
function log({ gender, address }) {
console.log({
name: this.name,
gender,
address,
})
}
const jack = {
name: 'Jack',
log: throttle(log, 3000),
}
Array.from({ length: 5 }, () => jack.log({ gender: 'Male', address: 'LA' }))
I made a npm package with some throttling functions:
npm install function-throttler
throttleAndQueue
Returns a version of your function that can be called at most every W milliseconds, where W is wait. Calls to your func that happen more often than W get queued up to be called every W ms
throttledUpdate
Returns a version of your function that can be called at most every W milliseconds, where W is wait. for calls that happen more often than W the last call will be the one called (last takes precedence)
throttle
limits your function to be called at most every W milliseconds, where W is wait. Calls over W get dropped
There is a library suited for this purpose, it's Backburner.js from Ember.
https://github.com/BackburnerJS/
You'd use it so.
var backburner = new Backburner(["task"]); //You need a name for your tasks
function saySomething(words) {
backburner.throttle("task", console.log.bind(console, words)
}, 1000);
}
function mainTask() {
"This will be said with a throttle of 1 second per word!".split(' ').map(saySomething);
}
backburner.run(mainTask)
This throttle function is build on ES6. Callback functions takes arguments (args), and still it works wrapped with throttle function. Be free to customize delay time according to your app needs. 1 time per 100ms is used for development mode, event "oninput" is just an example for frequent case of its use:
const callback = (...args) => {
console.count('callback throttled with arguments:', args);
};
throttle = (callback, limit) => {
let timeoutHandler = 'null'
return (...args) => {
if (timeoutHandler === 'null') {
timeoutHandler = setTimeout(() => {
callback(...args)
timeoutHandler = 'null'
}, limit)
}
}
}
window.addEventListener('oninput', throttle(callback, 100));
P.S. As #Anshul explained: throttling enforces a maximum number of times a function can be called over time. As in "execute this function at most once every 100 milliseconds."
In below example, try clicking the button multiple times, but the myFunc function would be executed only once in 3 sec.
The function throttle is passed with the function to be executed and the delay.It returns a closure, which is stored in obj.throttleFunc.
Now since obj.throttleFunc stores a closure, the value of isRunning is maintained inside it.
function throttle(func, delay) {
let isRunning;
return function(...args) {
let context = this; // store the context of the object that owns this function
if(!isRunning) {
isRunning = true;
func.apply(context,args) // execute the function with the context of the object that owns it
setTimeout(function() {
isRunning = false;
}, delay);
}
}
}
function myFunc(param) {
console.log(`Called ${this.name} at ${param}th second`);
}
let obj = {
name: "THROTTLED FUNCTION ",
throttleFunc: throttle(myFunc, 3000)
}
function handleClick() {
obj.throttleFunc(new Date().getSeconds());
}
button {
width: 100px;
height: 50px;
font-size: 20px;
}
<button onclick="handleClick()">Click me</button>
If we don't want the context or arguments to be passed, then a simpler
version of this would be as following:
function throttle(func, delay) {
let isRunning;
return function() {
if(!isRunning) {
isRunning = true;
func()
setTimeout(function() {
isRunning = false;
}, delay);
}
}
}
function myFunc() {
console.log('Called');
}
let throttleFunc = throttle(myFunc, 3000);
function handleClick() {
throttleFunc();
}
button {
width: 100px;
height: 50px;
font-size: 20px;
}
<button onclick="handleClick()">Click me</button>
I also want to suggest a simple solution for when there is only 1 function you know you will call (for example: Search)
here is what i did in my project
let throttle;
function search() {
if (throttle) {
clearTimeout(throttle);
}
throttle = setTimeout(() => {
sendSearchReq(str)
}, 500);
}
Search is called on input change event
function throttle(targetFunc, delay){
let lastFunc;
let lastTime;
return function(){
const _this = this;
const args = arguments;
if(!lastTime){
targetFunc.apply(_this, args);
lastTime = Date.now();
} else {
clearTimeout(lastFunc);
lastFunc = setTimeout(function(){
targetFunc.apply(_this, args);
lastTime = Date.now();
}, delay - (Date.now() - lastTime));
}
}
}
Try it :
window.addEventListener('resize', throttle(function() {
console.log('resize!!');
}, 200));
CodeSandbox
const { now } = Date;
export default function throttle(func, frameDuration) {
let timeout = null;
let latest;
const epoch = now();
function getDurationToNextFrame() {
const elapsed = now() - epoch;
const durationSinceLastFrame = elapsed % frameDuration;
return frameDuration - durationSinceLastFrame;
}
function throttled(...args) {
latest = () => {
func.apply(this, args);
};
if (!timeout) {
timeout = setTimeout(() => {
latest();
timeout = null;
}, getDurationToNextFrame());
}
}
return throttled;
}
Simple throttle function -
Note- Keep on clicking on the button , You'll see console log at first on click and then only after every 5 seconds until you're keep clicking.
HTML -
<button id='myid'>Click me</button>
Javascript -
const throttle = (fn, delay) => {
let lastTime = 0;
return (...args) => {
const currentTime = new Date().getTime();
if((currentTime - lastTime) < delay) {
return;
};
lastTime = currentTime;
return fn(...args);
}
};
document.getElementById('myid').addEventListener('click', throttle((e) => {
console.log('I am clicked');
}, 5000));
We can also implement using a flag-
var expensive = function(){
console.log("expensive functionnns");
}
window.addEventListener("resize", throttle(expensive, 500))
function throttle(expensiveFun, limit){
let flag = true;
return function(){
let context = this;
let args = arguments;
if(flag){
expensiveFun.apply(context, args);
flag = false;
setTimeout(function(){
flag = true;
}, limit);
}
}
}
Here is a bit modernized and simplified version of #clément-prévost answer
function throttle(func, wait, options = {}) {
let timeout = null;
let previous = 0;
const later = (...args) => {
previous = options.leading === false ? 0 : Date.now();
func(...args);
};
return (...args) => {
const now = Date.now();
if (!previous && options.leading === false) {
previous = now;
}
const remaining = wait - (now - previous);
if (remaining <= 0 || remaining > wait) {
if (timeout) {
clearTimeout(timeout);
timeout = null;
}
previous = now;
func(...args);
} else if (options.trailing !== false) {
clearTimeout(timeout);
timeout = setTimeout(() => later(...args), remaining);
}
};
}
function myFunc(a) {
console.log(`Log: ${a} ${this.val}`);
}
const myFuncThrottled = throttle(myFunc.bind({val: 42}), 1234, {leading: true, trailing: true})
myFuncThrottled(1)
myFuncThrottled(2)
myFuncThrottled(3)
function throttle(CB,ms=300,Id='Identifier for the callback(CB)'){
Id = Id || ""+CB
var N = throttle.N = throttle.N || {}; // Static variable N to store all callbacks ids and their status
if( N[Id] ) return; // already in the queue to run
N[Id] = 1; // add it the queue
setTimeout(()=>{
N[Id] = 0; // remove it from the queue
CB(); // finally call the function
}, ms);
}
for(var i=0;i<100;i++){
throttle(e=>console.log("Hi1"),1e3,'F1');
}
// will only output : Hi1
// this function guarantee the callback to run at least once
Some great solutions here already, but I was looking for a modern version with trailing (and optionally leading) executions, with the last passed arguments provided to each function call:
const throttle = (fn, wait=500, leading=true) => {
let prev, timeout, lastargs;
return (...args) => {
lastargs = args;
if (timeout) return;
timeout = setTimeout(() => {
timeout = null;
prev = Date.now();
// let's do this ... we'll release the stored args as we pass them through
fn.apply(this, lastargs.splice(0, lastargs.length));
// some fancy timing logic to allow leading / sub-offset waiting periods
}, leading ? prev && Math.max(0, wait - Date.now() + prev) || 0 : wait);
};
}
Usage:
x = throttle((...args) => console.log(...args));
let n = 0;
x(++n, 'boom');
x(++n, 'boom');
x(++n, 'boom');
if there will be more than one function defining them one by one would not be maintainable so i would suggest use a helper class to keep values for each
class slowDown {
constructor(cb,timeGap){
this.last = 0
this.run = function(){
let current = Date.now(),
shouldRun = (current - this.last) >= timeGap
if(shouldRun){
cb(current - this.last)
this.last = current
}
}
}
}
// example use
const press = new slowDown(timeElapsed => {
// define function here which you wanted to slow down
console.log("pressed after " + timeElapsed + " ms")
},750)
window.addEventListener("keydown",()=>{
press.run()
})
Below is the simplest throttle I could think of, in 13 LOC. It creates a timeout each time the function is called and cancels the old one. The original function is called with the proper context and arguments, as expected.
function throttle(fn, delay) {
var timeout = null;
return function throttledFn() {
window.clearTimeout(timeout);
var ctx = this;
var args = Array.prototype.slice.call(arguments);
timeout = window.setTimeout(function callThrottledFn() {
fn.apply(ctx, args);
}, delay);
}
}
// try it out!
window.addEventListener('resize', throttle(function() {
console.log('resize!!');
}, 200));

How to know browser idle time?

How can I track the browser idle time? I am using IE8.
I am not using any session management and don't want to handle it on server side.
Here is pure JavaScript way to track the idle time and when it reach certain limit do some action:
var IDLE_TIMEOUT = 60; //seconds
var _idleSecondsTimer = null;
var _idleSecondsCounter = 0;
document.onclick = function() {
_idleSecondsCounter = 0;
};
document.onmousemove = function() {
_idleSecondsCounter = 0;
};
document.onkeypress = function() {
_idleSecondsCounter = 0;
};
_idleSecondsTimer = window.setInterval(CheckIdleTime, 1000);
function CheckIdleTime() {
_idleSecondsCounter++;
var oPanel = document.getElementById("SecondsUntilExpire");
if (oPanel)
oPanel.innerHTML = (IDLE_TIMEOUT - _idleSecondsCounter) + "";
if (_idleSecondsCounter >= IDLE_TIMEOUT) {
window.clearInterval(_idleSecondsTimer);
alert("Time expired!");
document.location.href = "logout.html";
}
}
#SecondsUntilExpire { background-color: yellow; }
You will be auto logged out in <span id="SecondsUntilExpire"></span> seconds.
​This code will wait 60 seconds before showing alert and redirecting, and any action will "reset" the count - mouse click, mouse move or key press.
It should be as cross browser as possible, and straight forward. It also support showing the remaining time, if you add element to your page with ID of SecondsUntilExpire.
The above code should work fine, however has several downsides, e.g. it does not allow any other events to run and does not support multiply tabs. Refactored code that include both of these is following: (no need to change HTML)
var IDLE_TIMEOUT = 60; //seconds
var _localStorageKey = 'global_countdown_last_reset_timestamp';
var _idleSecondsTimer = null;
var _lastResetTimeStamp = (new Date()).getTime();
var _localStorage = null;
AttachEvent(document, 'click', ResetTime);
AttachEvent(document, 'mousemove', ResetTime);
AttachEvent(document, 'keypress', ResetTime);
AttachEvent(window, 'load', ResetTime);
try {
_localStorage = window.localStorage;
}
catch (ex) {
}
_idleSecondsTimer = window.setInterval(CheckIdleTime, 1000);
function GetLastResetTimeStamp() {
var lastResetTimeStamp = 0;
if (_localStorage) {
lastResetTimeStamp = parseInt(_localStorage[_localStorageKey], 10);
if (isNaN(lastResetTimeStamp) || lastResetTimeStamp < 0)
lastResetTimeStamp = (new Date()).getTime();
} else {
lastResetTimeStamp = _lastResetTimeStamp;
}
return lastResetTimeStamp;
}
function SetLastResetTimeStamp(timeStamp) {
if (_localStorage) {
_localStorage[_localStorageKey] = timeStamp;
} else {
_lastResetTimeStamp = timeStamp;
}
}
function ResetTime() {
SetLastResetTimeStamp((new Date()).getTime());
}
function AttachEvent(element, eventName, eventHandler) {
if (element.addEventListener) {
element.addEventListener(eventName, eventHandler, false);
return true;
} else if (element.attachEvent) {
element.attachEvent('on' + eventName, eventHandler);
return true;
} else {
//nothing to do, browser too old or non standard anyway
return false;
}
}
function WriteProgress(msg) {
var oPanel = document.getElementById("SecondsUntilExpire");
if (oPanel)
oPanel.innerHTML = msg;
else if (console)
console.log(msg);
}
function CheckIdleTime() {
var currentTimeStamp = (new Date()).getTime();
var lastResetTimeStamp = GetLastResetTimeStamp();
var secondsDiff = Math.floor((currentTimeStamp - lastResetTimeStamp) / 1000);
if (secondsDiff <= 0) {
ResetTime();
secondsDiff = 0;
}
WriteProgress((IDLE_TIMEOUT - secondsDiff) + "");
if (secondsDiff >= IDLE_TIMEOUT) {
window.clearInterval(_idleSecondsTimer);
ResetTime();
alert("Time expired!");
document.location.href = "logout.html";
}
}
The refactored code above is using local storage to keep track of when the counter was last reset, and also reset it on each new tab that is opened which contains the code, then the counter will be the same for all tabs, and resetting in one will result in reset of all tabs. Since Stack Snippets do not allow local storage, it's pointless to host it there so I've made a fiddle:
http://jsfiddle.net/yahavbr/gpvqa0fj/3/
Hope this is what you are looking for
jquery-idletimer-plugin
Too late to reply, but this might help someone to write clean and practical solution. This is an ideal solution, when you do not need to display time left for session expire. Good to ignore setInterval(), which keeps on running the script through out the application running time.
var inactivityTimeOut = 10 * 1000, //10 seconds
inactivitySessionExpireTimeOut = '';
setSessionExpireTimeOut();
function setSessionExpireTimeOut () {
'use strict';
clearSessionExpireTimeout();
inactivitySessionExpireTimeOut = setTimeout(function() {
expireSessionIdleTime();
}, inactivityTimeOut);
}
function expireSessionIdleTime () {
'use strict';
console.log('user inactive for ' + inactivityTimeOut + " seconds");
console.log('session expired');
alert('time expired');
clearSessionExpireTimeout();
document.location.href = "logout.html";
}
function clearSessionExpireTimeout () {
'use strict';
clearTimeout(inactivitySessionExpireTimeOut);
}
Running example: Timeout alert will be popped up in 10 seconds
Here's an approach using jquery as I needed to preserve existing keyboard events on the document.
I also needed to do different things at different idle times so I wrapped it in a function
var onIdle = function (timeOutSeconds,func){
//Idle detection
var idleTimeout;
var activity=function() {
clearTimeout(idleTimeout);
console.log('to cleared');
idleTimeout = setTimeout(func, timeOutSeconds * 1000);
}
$(document).on('mousedown mousemove keypress',activity);
activity();
}
onIdle(60*60,function(){
location.reload();
});
onIdle(30,function(){
if(currentView!=='welcome'){
loadView('welcome');
}
});
I needed a similar thing and created this :https://github.com/harunurhan/idlejs
It simple, configurable and powerful in a way, without any dependencies. Here's an example.
import { Idle } from 'idlejs/dist';
// with predefined events on `document`
const idle = new Idle()
.whenNotInteractive()
.within(60)
.do(() => console.log('IDLE'))
.start();
You can also use custom event targets and events
const idle = new Idle()
.whenNot([{
events: ['click', 'hover'],
target: buttonEl,
},
{
events: ['click', 'input'],
target: inputEl,
},
])
.within(10)
.do(() => called = true)
.start();
(Written in typescript and compiled to es5)

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