兼容 FF&IE 的替换鼠标选择文字方法

<script type="text/javascript">

function changes(obj){

var TextIn=document.getElementById("textin");

if(TextIn.createTextRange){
 //ie兼容
 TextIn.focus();
 document.selection.createRange().duplicate().text=obj;
}else{
 //firefox兼容
 var iStart = TextIn.selectionStart;
 var iEnd = TextIn.selectionEnd;
 TextIn.value=TextIn.value.substring(0,iStart)+obj+TextIn.value.substring(iEnd,TextIn.value.length);
 endRange=iStart+obj.length;
 TextIn.setSelectionRange(endRange,endRange);
}
}

</script>
<textarea cols="40" id="textin">选中这里的文字，然后点change试试看。</textarea>
<br />
<input type="button" onclick="changes('文字被替换了！')" value="change" />