打字机效果的两条实现路线：纯 CSS 与 JS-星海夜航

打字机效果——文字逐字出现、末尾光标闪烁。以前要做这个效果得上 JS，纯 CSS 其实也能实现。两种路线的代码各记一份，可直接使用。

纯 CSS：三层结构

把动画拆成三层：底层静止的文字、中间遮挡文字的背景、最上层的光标。初始时背景盖住全部文字、光标在最左；动画期间背景和光标以相同步伐从左往右移动；结束时背景不再遮挡文字，光标停在最右边闪烁。

<!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>Typing effect without js</title>
  <style>
    :root {
      /* number of characters */
      --steps: 345;
      /* animation time */
      --duration: 2.5s;
      --fontSize: 50px;
      --cursorSize: 20px;
    }
    .text {
      color: #333;;
      position: relative;
      display: inline-block;
      font-family: 'Courier New', Courier, monospace;
      font-size: var(--fontSize);
      line-height: 1;
    }
    .text::after {
      content: '';
      width: var(--cursorSize);
      height: var(--fontSize);
      background-color: black;
      z-index: 2;
      position: absolute;
      animation: blink 1s var(--duration) step-end infinite,
      moveCursor var(--duration) steps(var(--steps)) forwards;
    }
    .text::before {
      content: '';
      width: 100%;
      height: var(--fontSize);
      z-index: 1;
      position: absolute;
      background: linear-gradient(#fff, #fff) no-repeat top right;
      animation: showText var(--duration) steps(var(--steps)) forwards;
    }
    /* Cursor blink animation */
    @keyframes blink {
      0% {
        background-color: black;
      }
      50% {
        background-color: transparent;
      }
      100% {
        background-color: black;
      }
    }
    /* Cursor movement animation */
    @keyframes moveCursor {
      0% {
        left: 0%;
      }
      100% {
        left: 100%;
      }
    }
    /* background moving animation */
    @keyframes showText {
      0% {
        background-size: 100% 100%;
      }
      100% {
        background-size: 0% 100%;
      }
    }
  </style>
</head>
<body>
<div class="text">hello,world!</div>
</body>
</htm>

参数集中在 :root：–steps 是字符数、–duration 是动画时长，光标和文字尺寸各一个变量。文字内容改动后要同步改 –steps，否则背景移动步数和字符数对不齐。

这套方案唯一的好处是不需要 JS；缺点是目前只适合一行文本，多行理论上能实现但很麻烦。

JS 写法一：setTimeout 逐字追加

完整字符串存 JS 变量，每 200ms 用 slice 截取递增长度写回 div，末尾拼一个下划线当光标：

<!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>Typing effect with js</title>
</head>
<body>
<div style="font-size: 36px;" id="text">hello,world!</div>
<script>
  var str = 'In the past, to achieve an effect similar to typing on a computer,js+html was required. Today I will introduce a new method.';
  var i = 0;
  function typing(){
    var divTyping = document.getElementById('text');
    if (i <= str.length) {
      divTyping.innerHTML = str.slice(0, i++) + '_';
      setTimeout('typing()', 200);
    }
    else{
      divTyping.innerHTML = str;
    }
  }
  typing();
</script>
</body>
</html>

JS 写法二：隐藏元素 + setInterval + substring

思路相同，只是把原文藏在另一个隐藏 div 里，index 递增配合 setInterval 用 substring 截取：

<!DOCTYPE html>
<html>
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  <title>Typing effect with js</title>
  <style>
    .divcss5{word-wrap:break-word;font-size: 36px;}
  </style>
</head>
<body>
<div class="divcss5"  id="aa">
  In the past, to achieve an effect similar to typing on a computer, js+html was required. Today I will introduce a new method.This article mainly
</div>
<div style="display:none" id="w">
  In the past, to achieve an effect similar to typing on a computer, js+html was required. Today I will introduce a new method.This article mainly introduces pure html+css to achieve typing effect, which has certain reference value, you can learn about it. Provide all the code, you can use it directly.
</div>
<script language="javascript">
  var index=0;
  var word=document.getElementById("w").innerHTML;
  function type(){
    document.getElementById("aa").innerText = word.substring(0,index++);
  }
  setInterval(type, 200);
</script>
</body>
</html>