<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<style>
.progress4 {
display: block;
font: inherit;
height: 50px;
width: 300px;
pointer-events: none;
}
.btn {
margin-top: 30px;
}
</style>
<body>
<meter id="progress4" class="progress4" low="60" high="80" min="0" max="100" value="0"></meter>
<button id="btn" class="btn">点我一下嘛～</button>
</body>
<script>
'use strict';
let startTimestamp = (new Date()).getTime();
let currentPercentage = 0;
let maxPercentage = 100;
let countDelay = 100;
let timer = null;
let start = false;
const percentageChange = () => {
const currentTimestamp = (new Date()).getTime();
if (currentTimestamp - startTimestamp >= countDelay) {
currentPercentage++;
startTimestamp = (new Date()).getTime();
progress4.value = currentPercentage;
};
if (currentPercentage < maxPercentage) {
timer = window.requestAnimationFrame(percentageChange);
} else {
window.cancelAnimationFrame(timer);
};
};
const clickHander = () => {
if (!start) {
start = true;
percentageChange();
};
};
btn.addEventListener('click', clickHander);
</script>
</html>
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