React源码学习：requestIdleCallback
利用浏览器的空闲时间执行任务(P37-P38)
核心价值
利用浏览器的空闲时间执行任务，如果有优先级高的任务执行时，当前任务被终止，执行高级别的任务
基本用法
requestIdleCallback(function(deadline){
// deadline.timeRemaning() 获取浏览器的空余时间(ms)
})原理<什么是浏览器的空余时间>
- 1s 执行 60 帧，刚好觉得不卡顿，每一帧的时间在
1000/60 = 16.6ms - 当每一帧的执行时间小于16ms，就说明浏览器有空余时间
一个卡顿的任务
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Example RIC</title>
<style>
#box {
background: palevioletred;
padding: 20px;
margin-bottom: 10px;
}
</style>
</head>
<body>
<div id="box">box</div>
<button id="btn1">执行计算任务</button>
<button id="btn2">更改背景颜色</button>
<script>
var box = document.getElementById('box')
var btn1 = document.getElementById('btn1')
var btn2 = document.getElementById('btn2');
var number = 99999;
var value = 0;
function calc() {
while (number > 0) {
value = Math.random() < 0.5 ? Math.random() : Math.random()
console.log(value)
number--
}
}
btn1.onclick = function () {
calc()
}
btn2.onclick = function () {
box.style.background = 'green'
}
</script>
</body>
</html>用 requestIdleCallback解决这个问题
requestIdleCallback(calc)调用了这个的，优先级偏低的任务- 其它事件类任务：优先级高的任务
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Example RIC</title>
<style>
#box {
background: palevioletred;
padding: 20px;
margin-bottom: 10px;
}
</style>
</head>
<body>
<div id="box">box</div>
<button id="btn1">执行计算任务</button>
<button id="btn2">更改背景颜色</button>
<script>
var box = document.getElementById('box')
var btn1 = document.getElementById('btn1')
var btn2 = document.getElementById('btn2');
var number = 99999;
var value = 0;
function calc(deadline) {
while (number > 0 && deadline.timeRemaining() > 1) {
value = Math.random() < 0.5 ? Math.random() : Math.random()
console.log(value)
number--
}
requestIdleCallback(calc)
}
btn1.onclick = function () {
requestIdleCallback(calc)
}
btn2.onclick = function () {
box.style.background = 'green'
}
</script>
</body>
</html>参考