浏览器的5种Observer
IntersectionObserver
监听一个元素和可视区域相交部分的比例，然后再可视比例达到某个阀值的时候触发回调
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
#box1,
#box2 {
width: 100px;
height: 100px;
background: blue;
color: #fff;
position: relative;
}
#box1 {
top: 500px;
}
#box2 {
top: 800px;
}
</style>
</head>
<body>
<div id="box1">BOX11</div>
<div id="box2">BOX22</div>
<script>
// 监听一个元素和可视区域相交部分的比例，然后再可视比例达到某个阀值的时候触发回调
const intersectionObserver = new IntersectionObserver(
function (entries) {
console.log('info')
entries.forEach(item => {
console.log(item.target, item.intersectionRatio)
})
}, {
threshold: [0.5, 1]
}
)
intersectionObserver.observe(document.querySelector('#box1'))
// intersectionObserver.observe(document.querySelector('#box2'))
</script>
</body>
</html>MutationObserver
监听对元素的属性的修改、对它的子节点的增删改
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
#box {
width: 100px;
height: 100px;
background: blue;
position: relative;
}
</style>
</head>
<body>
<div id="box">
<button>光</button>
</div>
<script>
// 监听对元素的属性的修改、对它的子节点的增删改
setTimeout(() => {
box.style.background = 'pink'
}, 2000)
setTimeout(() => {
const dom = document.createElement('button')
dom.textContent = 'blog'
box.appendChild(dom)
}, 3000)
setTimeout(() => {
document.querySelectorAll('button')[0].remove()
}, 5000)
const mutationObserver = new MutationObserver((mutationsList) => {
console.log(mutationsList)
})
mutationObserver.observe(box, {
attributes: true,
childList: true
})
</script>
</body>
</html>ResizeObserver
监听大小的改变,当 width 、height 被修改时会触发回调
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
#box {
width: 100px;
height: 100px;
background: blue;
}
</style>
</head>
<body>
<div id="box"></div>
<script>
// 监听大小的改变,当width、height被修改时会触发回调
const box = document.querySelector('#box')
setTimeout(() => {
box.style.width = '200px'
}, 2000)
const resizeObserver = new ResizeObserver(entries => {
console.log('当前', entries)
})
resizeObserver.observe(box)
</script>
</body>
</html>PerformanceObserver
用于监听记录 performance 数据的行为,一旦记录了就会触发回调
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<button onclick="measureClick()">Measure</button>
<img src="https://cloudneedle-tv.oss-cn-hangzhou.aliyuncs.com/hs_tv/hs_logo/hslogo.png" />
<script>
// 用于监听记录performance数据的行为,一旦记录了就会触发回调
const performanceObserver = new PerformanceObserver(list => {
list.getEntries().forEach(entry => {
console.log(entry)
})
})
performanceObserver.observe({entryTypes: ['resource', 'mark', 'measure']})
// 用mark方法记录某个时间点
performance.mark('registered-observer')
function measureClick () {
// 用measure方法记录某个时间段
performance.measure('button clicked')
}
</script>
</body>
</html>ReportingObserver
监听过时的 api 、浏览器的一些干预行为的报告
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<button>测试</button>
<script>
// 监听过时的api、浏览器的一些干预行为的报告
const reportingObserver = new ReportingObserver((reports, observer) => {
for (const report of reports) {
// 上报
console.log(report.body)
}
}, {types: ['intervention', 'deprecation']})
reportingObserver.observe()
</script>
</body>
</html>参考
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