textarea输入框限制字数

<textarea onkeyup="checkLen(this)"></textarea> 

<div>您还可以输入 <span id="count">200</span> 个文字</div> 

<script type="text/javascript"> 

function checkLen(obj) {  

var maxChars = 200;//最多字符数  

if (obj.value.length > maxChars)  obj.value = obj.value.substring(0,maxChars);  

var curr = maxChars - obj.value.length;  

document.getElementByIdx_x("count").innerHTML = curr.toString(); 

} 

</script>