js限制文本框字数

 

<input type="text" onkeydown="keyDown(this,10,event);" />
    <script type="text/javascript">
        var keyDown = function (obj, count, evt) {
            if (evt.keyCode == 8) {
                return;
            }
            if (obj.value.length > count - 1) {
                evt.returnValue = false;
            }
        }
    </script>