javascript 输入框字符数提示,超出提示

<!————代码开始———–>

<div><input type=”text” id=”in” onkeyup=”tslx(this);” size=”100″ />

<br /><i id=”alt”></i></div>

<script type=”text/javascript”>

function len(s) {

var l = 0;

var a = s.split(“”);

for (var i=0;i<a.length;i++) {

if (a[i].charCodeAt(0)<299) {

l++;

} else {

l+=2;

}

}

return l;

}

function tslx(t,tl){

/*

t = input this

tl = 字符限制数; 默认 50个字符 25个汉字

*/

tl = tl || 50;

var v = t.value;

var txt = “已经输入” + len(v) + “字符”;

if( len(v) > tl){

txt += “,超出” + (len(v) – tl) + “字符”;

document.getElementById(“alt”).style.color = “red”;

}else{

txt += “,还能输入” + (tl – len(v)) + “字符”;

document.getElementById(“alt”).style.color = “”

}

document.getElementById(“alt”).innerHTML = txt;

}

</script>