网页顶部添加阅读进度条方法（适用于任何网页）

第一种方法

顶部添加 直接加入html，不需要分别放到css和js里

<!-- 进度条 -->
<style>
  progress {
    /* position: fixed;
    left: 0; */
    /* right: 0; */
    /* bottom: 0; */
    /* top: 0;
    width: 100%;
    text-align: center;
    height: 0.5rem;
    border: 1px solid #999;
    border-radius: 1rem;
    z-index: 5;
    -webkit-apperance: none; */
     position: fixed;
      left: 0;
      top: 0;
      z-index: 1000;
      width: 100%;
      height: 2px;
      -webkit-appearance: none;
      -moz-appearance: none;
      appearance: none;
      border: none;
      background-color: transparent;
      color: #35a935;
  }
 
 
  ::-webkit-progress-bar {
    background-color: #eee;
    border-radius: 1rem;
  }
 
  ::-webkit-progress-value {
    background-color: #169fe6ad;
    border-radius: 1rem;
  }
</style>
<script>
  // 生成元素并添加到文档尾部
  var progress = document.createElement('progress');
  progress.id = 'progress';
 
  document.body.appendChild(progress);
 
  // 计算当前页面的高度并赋值给进度条
  var H;
  window.onload = function () {
    progress.max = H = home.scrollHeight;
    progress.value = 0;
  }
 
  // 监听滚动，实时计算滚动条进度值
  window.onscroll = function () {
    var h = document.documentElement.scrollTop || document.body.scrollTop;
    progress.value = h;
    var radio = (h / H >= 1) ? 1 : h / H;
    progress.innerHTML = progress.title = Math.floor(100 * radio) + '%';
  }
</script>

第二种实现方式 （推荐方法）

html加入（html+js，js也可以单独拿出来）

<!-- 顶部进度条 -->
<progress id="content_progress" value="0"></progress>
 
<script>
document.addEventListener('DOMContentLoaded', function () {
      var winHeight = window.innerHeight,
            docHeight = document.documentElement.scrollHeight,
            progressBar = document.querySelector('#content_progress');
      progressBar.max = docHeight - winHeight;
      progressBar.value = window.scrollY;
 
      document.addEventListener('scroll', function () {
            progressBar.max = document.documentElement.scrollHeight - window.innerHeight;
            progressBar.value = window.scrollY;
      });
});
</script>

css

/* 顶部进度条css */
#content_progress {
      /* Positioning */
      position: fixed;
      left: 0;
      top: 0;
      z-index: 1000;
      width: 100%;
      height: 2px;
      -webkit-appearance: none;
      -moz-appearance: none;
      appearance: none;
      border: none;
      background-color: transparent;
      color: #35a935;
}
 
#content_progress::-webkit-progress-bar {
      background-color: transparent;
}
 
#content_progress::-webkit-progress-value {
      background-color: #35a935;
}
 
#content_progress::-moz-progress-bar {
      background-color: #35a935;
}