JS实现选择TextArea内文本的方法

<script type="text/javascript">  function select_field(id){    document.getElementById(id).focus();    document.getElementById(id).select();  }  function init(){    select_field('text1');  }  onload=init;</script><form>This field gets selected onload:<br/><input type="text" name="text1" id="text1" value="some text" /><br/><textarea name="textarea1" id="textarea1" rows="9" cols="50" wrap="off">Some longcontent in here.abcd efgh abcd efgh abcd efghabcd efgh abcd efgh abcd efghabcd efgh abcd efgh abcd efgh</textarea><br/><input type="button" value="Select text" onclick="select_field('textarea1')"></form>