textarea自适应高度

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<h3>textarea自适应高度</h3>
<textarea style='border: 1px solid #94BBE2;width:100%;' rows=15 onpropertychange='this.style.posHeight=this.scrollHeight' id=textarea onfocus='textarea.style.posHeight=this.scrollHeight'>
<br>
<Br>
</textarea>
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