JavaScript 实现滑动进度条功能详解

<!DOCTYPE html>
<html>
<head>
 <meta charset="utf-8" />
 <title>js滑动进度条效果</title>
 <style>
  *{margin:0;padding:0;user-select:none;}
  .progress-bar{position:relative;height:10px;width:400px;margin:200px auto;background:#ebeef5;border-radius:10px;}
  .progress-bar .pro-bar{position:absolute;left:0;height:10px;width:10px;background:#409eff;}
  .progress-bar .min-num{position:absolute;left:-20px;top:-5px;}
  .progress-bar .max-num{position:absolute;right:-40px;top:-5px;}
  .progress-bar .block {position:absolute;height:30px;width:10px;background:#ccc;top:-10px;border-radius:10px;}
  .progress-bar .block div{position:absolute;display:none;left:-20px;top:-45px;width:50px;height:30px;text-align:center;line-height:30px;background:#ccc;border-radius:20px;}
  .progress-bar .block:hover div{display:block;font-size:10%;color:#fff;background:#409eff;}
 </style>
</head>
<body>
 <div class="progress-bar">
 <span class="min-num">0</span>
 <span class="max-num">100</span>
 <div class="pro-bar"></div>
 <div class="block">
  <div>0</div>
 </div>
 </div>
</body>
<script>
 (function(){
 let moveBlock = document.querySelector('.block');
 let proBar = document.querySelector('.pro-bar');
 let flag = false;
 let startX = null;
 let moveMax = (400 - 10); // 背景条宽度减去滑块的宽度
 moveBlock.onmousedown = function(e){
  startX = e.pageX;
  moveBlock.style.left ? moveBlock.style.left : moveBlock.style.left = '0px';
  let startLeft = parseInt(moveBlock.style.left);
  document.onmousemove = function(e){
  let moveX = (e.pageX - startX) > 0 ? true : false;
  let moveSection = startLeft + (e.pageX - startX);
  // 限定移动范围
  if (moveSection >= 0 && moveSection <= moveMax) {
   let percent = ((startLeft + (e.pageX - startX)) / moveMax).toFixed(4) * 100;
   percent.toString().length > 5 ? percent = percent.toString().subStr(0, 5) : percent = percent.toString();
   moveBlock.style.left = startLeft + (e.pageX - startX) + 'px';
   proBar.style.width = moveBlock.style.left;
   moveBlock.querySelector('div').innerText = percent + '%';
  }
  };
 };
 // 鼠标松开移除事件
 moveBlock.onmouseup = function(){
  document.onmousemove = null;
 };
 })();
</script>
</html>