我对＆＃34; debouncing＆＃34;感兴趣javascript中的函数，写在这里：http://davidwalsh.name/javascript-debounce-function
不幸的是，代码的解释不够清楚，我无法理解。任何人都可以帮我弄清楚它是如何工作的（我在下面留下了我的评论）。总之，我真的不明白这是如何工作的
// Returns a function, that, as long as it continues to be invoked, will not
// be triggered. The function will be called after it stops being called for
// N milliseconds.
function debounce(func, wait, immediate) {
var timeout;
return function() {
var context = this, args = arguments;
var later = function() {
timeout = null;
if (!immediate) func.apply(context, args);
};
var callNow = immediate && !timeout;
clearTimeout(timeout);
timeout = setTimeout(later, wait);
if (callNow) func.apply(context, args);
};
};
编辑：复制的代码段之前在错误的位置callNow。
答案 0 :(得分：99)
问题中的代码与链接中的代码略有不同。在链接中，在创建新的提示之前检查(immediate && !timeout)。拥有它后立即模式永远不会开火。我已经更新了我的答案，以便从链接中注释工作版本。
function debounce(func, wait, immediate) {
// 'private' variable for instance
// The returned function will be able to reference this due to closure.
// Each call to the returned function will share this common timer.
var timeout;
// Calling debounce returns a new anonymous function
return function() {
// reference the context and args for the setTimeout function
var context = this,
args = arguments;
// Should the function be called now? If immediate is true
// and not already in a timeout then the answer is: Yes
var callNow = immediate && !timeout;
// This is the basic debounce behaviour where you can call this
// function several times, but it will only execute once
// [before or after imposing a delay].
// Each time the returned function is called, the timer starts over.
clearTimeout(timeout);
// Set the new timeout
timeout = setTimeout(function() {
// Inside the timeout function, clear the timeout variable
// which will let the next execution run when in 'immediate' mode
timeout = null;
// Check if the function already ran with the immediate flag
if (!immediate) {
// Call the original function with apply
// apply lets you define the 'this' object as well as the arguments
// (both captured before setTimeout)
func.apply(context, args);
}
}, wait);
// Immediate mode and no wait timer? Execute the function..
if (callNow) func.apply(context, args);
}
}
/////////////////////////////////
// DEMO:
function onMouseMove(e){
console.clear();
console.log(e.x, e.y);
}
// Define the debounced function
var debouncedMouseMove = debounce(onMouseMove, 50);
// Call the debounced function on every mouse move
window.addEventListener('mousemove', debouncedMouseMove);
答案 1 :(得分：52)
这里需要注意的重要一点是，debounce会产生一个功能，它被关闭＆＃34; timeout变量。 timeout变量在生成函数的每次调用期间都可以访问，即使debounce本身已经返回，可以更改不同的调用。
debounce的一般想法如下：
第一点只是var timeout;，它确实只是undefined。幸运的是，clearTimeout对其输入相当宽松：传递undefined计时器标识符会导致它无所事事，它不会抛出错误或其他东西。
第二点由生成的函数完成。它首先在变量中存储有关调用的一些信息（this上下文和arguments），以便稍后可以将这些信息用于去抖动调用。然后它会清除超时（如果有一组），然后创建一个新的超时使用setTimeout替换它。 请注意，这会覆盖timeout的值，并且此值会在多个函数调用中持续存在！这允许去抖实际工作：如果多次调用该函数，timeout是用新计时器多次覆盖。如果不是这种情况，多次通话将导致启动多个计时器，其中所有保持活动状态 - 这些通话只会被延迟，但不会被去抖动。
第三点是在超时回调中完成的。它取消设置timeout变量并使用存储的调用信息进行实际函数调用。
immediate标志应该控制是否应该在之前调用或在定时器之后调用。如果是false，则在计时器被击中之后才会调用原始函数。如果它是true，则原始函数首先被调用，并且在计时器被命中之前不再被调用。
但是，我确实认为if (immediate && !timeout)检查错误：timeout刚刚设置为setTimeout返回的计时器标识符，因此!timeout始终为{{1}在那一点上，因此永远不会调用该函数。 The current version of underscore.js似乎有一个稍微不同的检查，在调用false之前评估immediate && !timeout 。 （算法也有点不同，例如它没有使用setTimeout。）这就是为什么你应该总是尝试使用最新版本的库。 ： - ）
答案 2 :(得分：26)
去抖动函数在调用时不会执行，它们会在执行前等待一段可配置的持续时间暂停调用;每次新调用都会重新启动计时器。
限制函数执行，然后等待一段可配置的持续时间，然后才有资格再次触发。
去抖是非常适合按键事件;当用户开始输入然后暂停时，您将所有按键提交为单个事件，从而减少处理调用。
Throttle非常适合您只想让用户在一段时间内调用一次的实时端点。
查看Underscore.js的实施方案。
答案 3 :(得分：18)
我在一篇名为 Demistifying Debounce in JavaScript 的文章中写了一篇文章，其中我准确地解释了how a debounce function works并包含了一个演示。
我也没完全理解当我第一次遇到debounce功能时它是如何工作的。虽然尺寸相对较小，但它们实际上采用了一些非常先进的JavaScript概念！掌握范围，闭包和setTimeout方法将有所帮助。
话虽如此，下面是我在上面引用的帖子中解释和演示的基本去抖函数。
成品
// Create JD Object
// ----------------
var JD = {};
// Debounce Method
// ---------------
JD.debounce = function(func, wait, immediate) {
var timeout;
return function() {
var context = this,
args = arguments;
var later = function() {
timeout = null;
if ( !immediate ) {
func.apply(context, args);
}
};
var callNow = immediate && !timeout;
clearTimeout(timeout);
timeout = setTimeout(later, wait || 200);
if ( callNow ) {
func.apply(context, args);
}
};
};
解释
// Create JD Object
// ----------------
/*
It's a good idea to attach helper methods like `debounce` to your own
custom object. That way, you don't pollute the global space by
attaching methods to the `window` object and potentially run in to
conflicts.
*/
var JD = {};
// Debounce Method
// ---------------
/*
Return a function, that, as long as it continues to be invoked, will
not be triggered. The function will be called after it stops being
called for `wait` milliseconds. If `immediate` is passed, trigger the
function on the leading edge, instead of the trailing.
*/
JD.debounce = function(func, wait, immediate) {
/*
Declare a variable named `timeout` variable that we will later use
to store the *timeout ID returned by the `setTimeout` function.
*When setTimeout is called, it retuns a numeric ID. This unique ID
can be used in conjunction with JavaScript's `clearTimeout` method
to prevent the code passed in the first argument of the `setTimout`
function from being called. Note, this prevention will only occur
if `clearTimeout` is called before the specified number of
milliseconds passed in the second argument of setTimeout have been
met.
*/
var timeout;
/*
Return an anomymous function that has access to the `func`
argument of our `debounce` method through the process of closure.
*/
return function() {
/*
1) Assign `this` to a variable named `context` so that the
`func` argument passed to our `debounce` method can be
called in the proper context.
2) Assign all *arugments passed in the `func` argument of our
`debounce` method to a variable named `args`.
*JavaScript natively makes all arguments passed to a function
accessible inside of the function in an array-like variable
named `arguments`. Assinging `arguments` to `args` combines
all arguments passed in the `func` argument of our `debounce`
method in a single variable.
*/
var context = this, /* 1 */
args = arguments; /* 2 */
/*
Assign an anonymous function to a variable named `later`.
This function will be passed in the first argument of the
`setTimeout` function below.
*/
var later = function() {
/*
When the `later` function is called, remove the numeric ID
that was assigned to it by the `setTimeout` function.
Note, by the time the `later` function is called, the
`setTimeout` function will have returned a numeric ID to
the `timeout` variable. That numeric ID is removed by
assiging `null` to `timeout`.
*/
timeout = null;
/*
If the boolean value passed in the `immediate` argument
of our `debouce` method is falsy, then invoke the
function passed in the `func` argument of our `debouce`
method using JavaScript's *`apply` method.
*The `apply` method allows you to call a function in an
explicit context. The first argument defines what `this`
should be. The second argument is passed as an array
containing all the arguments that should be passed to
`func` when it is called. Previously, we assigned `this`
to the `context` variable, and we assigned all arguments
passed in `func` to the `args` variable.
*/
if ( !immediate ) {
func.apply(context, args);
}
};
/*
If the value passed in the `immediate` argument of our
`debounce` method is truthy and the value assigned to `timeout`
is falsy, then assign `true` to the `callNow` variable.
Otherwise, assign `false` to the `callNow` variable.
*/
var callNow = immediate && !timeout;
/*
As long as the event that our `debounce` method is bound to is
still firing within the `wait` period, remove the numerical ID
(returned to the `timeout` vaiable by `setTimeout`) from
JavaScript's execution queue. This prevents the function passed
in the `setTimeout` function from being invoked.
Remember, the `debounce` method is intended for use on events
that rapidly fire, ie: a window resize or scroll. The *first*
time the event fires, the `timeout` variable has been declared,
but no value has been assigned to it - it is `undefined`.
Therefore, nothing is removed from JavaScript's execution queue
because nothing has been placed in the queue - there is nothing
to clear.
Below, the `timeout` variable is assigned the numerical ID
returned by the `setTimeout` function. So long as *subsequent*
events are fired before the `wait` is met, `timeout` will be
cleared, resulting in the function passed in the `setTimeout`
function being removed from the execution queue. As soon as the
`wait` is met, the function passed in the `setTimeout` function
will execute.
*/
clearTimeout(timeout);
/*
Assign a `setTimout` function to the `timeout` variable we
previously declared. Pass the function assigned to the `later`
variable to the `setTimeout` function, along with the numerical
value assigned to the `wait` argument in our `debounce` method.
If no value is passed to the `wait` argument in our `debounce`
method, pass a value of 200 milliseconds to the `setTimeout`
function.
*/
timeout = setTimeout(later, wait || 200);
/*
Typically, you want the function passed in the `func` argument
of our `debounce` method to execute once *after* the `wait`
period has been met for the event that our `debounce` method is
bound to (the trailing side). However, if you want the function
to execute once *before* the event has finished (on the leading
side), you can pass `true` in the `immediate` argument of our
`debounce` method.
If `true` is passed in the `immediate` argument of our
`debounce` method, the value assigned to the `callNow` variable
declared above will be `true` only after the *first* time the
event that our `debounce` method is bound to has fired.
After the first time the event is fired, the `timeout` variable
will contain a falsey value. Therfore, the result of the
expression that gets assigned to the `callNow` variable is
`true` and the function passed in the `func` argument of our
`debounce` method is exected in the line of code below.
Every subsequent time the event that our `debounce` method is
bound to fires within the `wait` period, the `timeout` variable
holds the numerical ID returned from the `setTimout` function
assigned to it when the previous event was fired, and the
`debounce` method was executed.
This means that for all subsequent events within the `wait`
period, the `timeout` variable holds a truthy value, and the
result of the expression that gets assigned to the `callNow`
variable is `false`. Therefore, the function passed in the
`func` argument of our `debounce` method will not be executed.
Lastly, when the `wait` period is met and the `later` function
that is passed in the `setTimeout` function executes, the
result is that it just assigns `null` to the `timeout`
variable. The `func` argument passed in our `debounce` method
will not be executed because the `if` condition inside the
`later` function fails.
*/
if ( callNow ) {
func.apply(context, args);
}
};
};
答案 4 :(得分：2)
我们现在都在使用 Promises
我见过的许多实现都使问题过于复杂或存在其他卫生问题。现在是 2021 年，我们已经使用 Promises 很长时间了——这也是有充分理由的。 Promise 清理异步程序并减少发生错误的机会。在这篇文章中，我们将编写自己的 debounce。此实现将 -
我们用它的两个参数编写 debounce，task 去抖动，以及延迟的毫秒数，ms。我们为其本地状态引入了一个本地绑定，t -
function debounce (task, ms) {
let t = { promise: null, cancel: _ => void 0 }
return async (...args) => {
try {
t.cancel()
t = deferred()
await t.promise
await task(...args)
}
catch (_) { /* prevent memory leak */ }
}
}
我们依赖于一个可重用的 deferred 函数，该函数创建了一个在 ms 毫秒内解析的新承诺。它引入了两个本地绑定，promise 本身，cancel 它的能力 -
function deferred (ms) {
let cancel, promise = new Promise((resolve, reject) => {
cancel = reject
setTimeout(resolve, ms)
})
return { promise, cancel }
}
点击计数器示例
在第一个示例中，我们有一个按钮来计算用户的点击次数。事件侦听器使用 debounce 附加，因此计数器仅在指定的持续时间后递增 -
// debounce, deferred
function debounce (task, ms) { let t = { promise: null, cancel: _ => void 0 }; return async (...args) => { try { t.cancel(); t = deferred(ms); await t.promise; await task(...args); } catch (_) { console.log("cleaning up cancelled promise") } } }
function deferred (ms) { let cancel, promise = new Promise((resolve, reject) => { cancel = reject; setTimeout(resolve, ms) }); return { promise, cancel } }
// dom references
const myform = document.forms.myform
const mycounter = myform.mycounter
// event handler
function clickCounter (event) {
mycounter.value = Number(mycounter.value) + 1
}
// debounced listener
myform.myclicker.addEventListener("click", debounce(clickCounter, 1000))<form id="myform">
<input name="myclicker" type="button" value="click" />
<output name="mycounter">0</output>
</form>实时查询示例，“自动完成”
在第二个示例中，我们有一个带有文本输入的表单。我们的 search 查询使用 debounce -
// debounce, deferred
function debounce (task, ms) { let t = { promise: null, cancel: _ => void 0 }; return async (...args) => { try { t.cancel(); t = deferred(ms); await t.promise; await task(...args); } catch (_) { console.log("cleaning up cancelled promise") } } }
function deferred (ms) { let cancel, promise = new Promise((resolve, reject) => { cancel = reject; setTimeout(resolve, ms) }); return { promise, cancel } }
// dom references
const myform = document.forms.myform
const myresult = myform.myresult
// event handler
function search (event) {
myresult.value = `Searching for: ${event.target.value}`
}
// debounced listener
myform.myquery.addEventListener("keypress", debounce(search, 1000))<form id="myform">
<input name="myquery" placeholder="Enter a query..." />
<output name="myresult"></output>
</form>答案 5 :(得分：1)
你想要做的是：如果你试图一个接一个地调用一个函数，第一个应该取消并且新的应该等待给定的超时然后执行。那么实际上你需要一些方法来取消第一个函数的超时？但是怎么样？ 您可以调用该函数，并传递返回的timeout-id，然后将该ID传递给任何新函数。但上面的解决方案更优雅。
它的作用是有效地使timeout变量在返回函数的范围内可用。所以，当一个＆＃39;调整大小＆＃39;如果事件被触发，则不会再次调用debounce()，因此timeout内容不会更改（！），并且仍可用于＆＃34;下一个函数调用＆＃34;。
这里的关键基本上是我们每次调整resize事件时调用内部函数。也许更清楚的是我们是否想象所有resize-events都在一个数组中：
var events = ['resize', 'resize', 'resize'];
var timeout = null;
for (var i = 0; i < events.length; i++){
if (immediate && !timeout) func.apply(this, arguments);
clearTimeout(timeout); // does not do anything if timeout is null.
timeout = setTimeout(function(){
timeout = null;
if (!immediate) func.apply(this, arguments);
}
}
您看到timeout可用于下一次迭代吗？
在我看来，没有理由将this重命名为content和arguments重命名为args。
答案 6 :(得分：1)
javascript中的简单反跳方法
<!-- Basic HTML -->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>Debounce Method</title>
</head>
<body>
<button type="button" id="debounce">Debounce Method</button><br />
<span id="message"></span>
</body>
</html>
// JS File
var debouncebtn = document.getElementById('debounce');
function debounce(func, delay){
var debounceTimer;
return function () {
var context = this, args = arguments;
clearTimeout(debounceTimer);
debounceTimer = setTimeout(function() {
func.apply(context, args)
}, delay);
}
}
// Driver Code
debouncebtn.addEventListener('click', debounce(function() {
document.getElementById('message').innerHTML += '<br/> Button only triggeres is every 3 secounds how much every you fire an event';
console.log('Button only triggeres in every 3 secounds how much every you fire an event');
},3000))
运行时示例JSFiddle：https://jsfiddle.net/arbaazshaikh919/d7543wqe/10/
答案 7 :(得分：0)
这是一个变体，它总是在第一次调用去抖动功能时触发它，并带有更具描述性的变量：
function debounce(fn, wait = 1000) {
let debounced = false;
let resetDebouncedTimeout = null;
return function(...args) {
if (!debounced) {
debounced = true;
fn(...args);
resetDebouncedTimeout = setTimeout(() => {
debounced = false;
}, wait);
} else {
clearTimeout(resetDebouncedTimeout);
resetDebouncedTimeout = setTimeout(() => {
debounced = false;
fn(...args);
}, wait);
}
}
};
答案 8 :(得分：0)
简单的防抖动功能：-
HTML：-
<button id='myid'>Click me</button>
JavaScript：-
function debounce(fn, delay) {
let timeoutID;
return function(...args){
if(timeoutID) clearTimeout(timeoutID);
timeoutID = setTimeout(()=>{
fn(...args)
}, delay);
}
}
document.getElementById('myid').addEventListener('click', debounce(() => {
console.log('clicked');
},2000));