js实现字符中文汉字=两个字符

<input type="text" id="txt">

//字符串截取
function getByteVal(val, max) {
	var returnValue = '';
	var byteValLen = 0;
	for (var i = 0; i < val.length; i++) {
	if (val[i].match(/[^\x00-\xff]/ig) != null)
	byteValLen += 2;
	else
	byteValLen += 1;
	if (byteValLen > max)
	break;
	returnValue += val[i];
	}
	return returnValue;
}
$('#txt').bind('keyup',function(){
	var val=this.value;
	if(val.replace(/[^\x00-\xff]/g,"**").length>14){
	this.value=getByteVal(val,14)
	}
})