Javascript 实现 Textarea 自动伸缩，兼容IE6、IE7、IE8、IE9...

直接上代码

<textarea id="textarea1" onkeyup="AutoExpand(this)" onfocus="AutoExpand(this)">

<script type="text/javascript">
  var InitHeight = 20;
  function AutoExpand(e) {
    var HideTextarea = document.getElementById("__hidetextarea");
    if (!HideTextarea) {
      HideTextarea = document.createElement("textarea");
      HideTextarea.id = "__hidetextarea";
      HideTextarea.style.borderWidth = 0;
      document.body.appendChild(HideTextarea);
    }
    HideTextarea.value = e.value;
    HideTextarea.style.height = "0px";
    HideTextarea.style.overflow = "hidden";
    var x = HideTextarea.scrollHeight + "必须先计算下scrollHeight的值，否则，scrollHeight 的值将固定？";
    delete x;
    e.style.height = Math.max(Math.max(InitHeight,20), HideTextarea.scrollHeight) + "px";
  }
</script>

结语

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