js 验证密码强弱的小例子

页面代码：

代码如下:
<table>
        <tr><td><input type="text" id="txtPwd" /></td></tr>
        <tr><td>
            <table id="pwdLever">
                <tr>
                    <td>弱</td>
                    <td>中</td>
                    <td>强</td>
                </tr>
            </table>
        </td></tr>
    </table>

样式：

代码如下:
<style type="text/css">
        #pwdLever td
        {
           background-color:Gray;
           width:45px;
           text-align:center;
        }
    </style>

js代码：

代码如下:
<script type="text/javascript">
        window.onload = function () {
            var textInput = document.getElementById("txtPwd");
            //给密码输入框 注册键放开事件
            textInput.onkeyup = function () {
                var pwdValue = this.value;
                var num = pwdChange(pwdValue);
                var tds = document.getElementById("pwdLever").getElementsByTagName("td");
                //修改密码颜色
                if (num == 0 || num == 1) {
                    tds[0].style.backgroundColor = "red";
                    tds[1].style.backgroundColor = "gray";