如果只是單純地想限制 textarea 中的字數，不想寫太多的話，可用：
<textarea οnkeyup="this.value = this.value.slice(0, 80)"></textarea>
或
<textarea οnkeyup="this.value = this.value.substring(0, 80)"></textarea>
o 在 textarea 的 onkeyup 中檢查字數之方法：
.....
<script language="javascript" type="text/javascript">
function DjCheckMaxlength(oInObj)
{
var iMaxLen = parseInt(oInObj.getAttribute('maxlength'));
var iCurLen = oInObj.value.length;
if ( oInObj.getAttribute && iCurLen > iMaxLen )
{
oInObj.value = oInObj.value.substring(0, iMaxLen);
}
} //@ END OF DjCheckMaxlength()
</script>
.....
<textarea maxlength="80" οnkeyup="return DjCheckMaxlength(this);"></textarea>
.....
o 設定好自動去檢查所有的 textarea 之方法：
.....
<head>
<script language="javascript" type="text/javascript">
function DjTextArea_AddMaxlengthAttr()
{
var aX = document.getElementsByTagName_r('textarea');
for ( var iI = 0; aX.length > iI; iI++ )
{
if ( aX[iI].getAttribute('maxlength') )
{
aX[iI].onkeyup = aX[iI].onchange = DjTextArea_CheckMaxlength;
}
}
} //@ END OF DjTextArea_AddMaxlengthAttr()
function DjTextArea_CheckMaxlength()
{
var iMaxLen = parseInt(this.getAttribute('maxlength'));
var iCurLen = this.value.length;
if ( this.getAttribute && iCurLen > iMaxLen )
{
this.value = this.value.substring(0, iMaxLen);
}
} //@ END OF DjTextArea_CheckMaxlength()
</script>
</head>
.....
<body οnlοad="DjTextArea_AddMaxlengthAttr();">
首先在textarea 上定义一个 maxlength 属性：
<textarea rows="3" cols="40" maxlength="200" οnkeydοwn="checklength(this);"></textarea>
然后添加这个方法就行了！
function checklength(obj) {
var max = obj.maxlength;
if(max == null || max == "" || max == undefined) {
return;
}
if(obj.value.length > max) {
alert("请不要超过最大长度:" + max);
obj.value=obj.value.substring(0,(max-1));
return;
}
}
