复制文本框里内容的js代码

<script type="text/javascript">
function copyit(){
document.all.text.select();
document.execCommand("copy");
alert("复制成功");
}
</script>
<TEXTAREA cols=80 name=text rows=22>这里是将要复制的内容
<input onclick="copyit()" name="select" type="button" value="复制" />