评估用户输入密码的强度-KnockoutJS入门指南

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我们来看看如果使用Knockout更简单的来实现密码强度的验证。

原有代码请查看：
```
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title></title>
</head>
<body>
    <script type="text/javascript">
        //CharMode函数 
function CharMode(iN) {
            if (iN >=48&& iN <=57) //数字
return1;
            if (iN >=65&& iN <=90) //大写字母
return2;
            if (iN >=97&& iN <=122) //小写
return4;
            else
                return8; //特殊字符 
        }

//bitTotal函数 
function bitTotal(num) {
            modes =0;
            for (i =0; i <4; i++) {
                if (num &1) modes++;
                num >>>=1;
            }
            return modes;
        }

//checkStrong函数 
function checkStrong(sPW) {
            if (sPW.length <=4)
                return0; //密码太短
            Modes =0;
            for (i =0; i < sPW.length; i++) {
                Modes |= CharMode(sPW.charCodeAt(i));
            }
            return bitTotal(Modes);
        }

//pwStrength函数 
function pwStrength(pwd) {
            O_color ="#eeeeee";
            L_color ="#FF0000";
            M_color ="#FF9900";
            H_color ="#33CC00";
            if (pwd ==null|| pwd =='') {
                Lcolor = Mcolor = Hcolor = O_color;
            } else {
                S_level = checkStrong(pwd);
                switch (S_level) {
                    case0:
                        Lcolor = Mcolor = Hcolor = O_color;
                    case1:
                        Lcolor = L_color;
                        Mcolor = Hcolor = O_color;
                        break;
                    case2:
                        Lcolor = Mcolor = M_color;
                        Hcolor = O_color;
                        break;
                    default:
                        Lcolor = Mcolor = Hcolor = H_color;
                }

//获取密码强度
Page.Utility.Registration.getPasswordLevel = function (password) {
    if (password == null || password == '')
        return 0;

if (password.length <= 4)
        return 0; //密码太短

var Modes = 0;
    for (i = 0; i < password.length; i++) {
        Modes |= CharMode(password.charCodeAt(i));
    }
    return bitTotal(Modes);

//CharMode函数 
    function CharMode(iN) {
        if (iN >= 48 && iN <= 57) //数字
            return 1;
        if (iN >= 65 && iN <= 90) //大写字母
            return 2;
        if (iN >= 97 && iN <= 122) //小写
            return 4;
        else
            return 8; //特殊字符 
    }

//bitTotal函数
    function bitTotal(num) {
        modes = 0;
        for (i = 0; i < 4; i++) {
            if (num & 1) modes++;
            num >>>= 1;
        }
        return modes;
    }
};
```
然后来创建View Model，但是引用Knockout之前，我们首先要引用Knockout的Js类库（具体介绍请查看Knockout应用开发指南的系列教程）
View model代码如下：
```
var viewModel = {
    Password: ko.observable(""),
    Ocolor: "#eeeeee"
};
```
对于密码强度以及颜色的值依赖于密码字符串的值，所以我们需要为他们声明依赖属性，代码如下：
```
viewModel.PasswordLevel = ko.dependentObservable(function () {
    return Page.Utility.Registration.getPasswordLevel(this.Password());
}, viewModel);

viewModel.Lcolor = ko.dependentObservable(function () {
    //根据密码强度判断第一个格显示的背景色
    return this.PasswordLevel() == 0 ? this.Ocolor : (this.PasswordLevel() == 1 ? "#FF0000" : (this.PasswordLevel() == 2 ? "#FF9900" : "#33CC00"))
}, viewModel);

viewModel.Mcolor = ko.dependentObservable(function () {
    //根据密码强度判断第二个格显示的背景色
    return this.PasswordLevel() < 2 ? this.Ocolor : (this.PasswordLevel() == 2 ? "#FF9900" : "#33CC00")
}, viewModel);

viewModel.Hcolor = ko.dependentObservable(function () {
    //根据密码强度判断第三个格显示的背景色
    return this.PasswordLevel() < 3 ? this.Ocolor : "#33CC00"
}, viewModel);
```
然后使用applyBindings方法将view model绑定到该页面，你可以使用jQuery的ready函数来执行该绑定代码，也可以在页面最下方执行绑定代码，我们这里使用了jQuery，代码如下：
```
$((function () {
    ko.applyBindings(viewModel);
}));
```
最后，我们再看看这些值怎么动态绑定到HTML元素上的，请查看如下代码（其中使用了afterkeydown代替了onKeyUp和onBlur）：
```
<form name="form1" action="">
输入密码:
<input type="text" size="10" data-bind="value:Password, valueUpdate: 'afterkeydown'">
<br>
密码强度:
<table width="217" border="1" cellspacing="0" cellpadding="1" bordercolor="#cccccc"
    height="23" style='display: inline'>
    <tr align="center" bgcolor="#eeeeee">
        <td width="50"data-bind="style: { backgroundColor: Lcolor }">弱</td>
        <td width="50"data-bind="style: { backgroundColor: Mcolor }">中</td>
        <td width="50"data-bind="style: { backgroundColor: Hcolor }">强</td>
    </tr>
</table>
</form>
```
然后就OK，运行代码查看，一模一样的功能展示出来了。

如果去掉为验证而改善的代码，总代码肯定是比原有的方式少的。

完整版代码如下：
```
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
    <script type="text/javascript" src="http://knockoutjs.com/js/jquery-1.4.2.min.js"></script>
    <script type="text/javascript" src="http://knockoutjs.com/js/jquery.tmpl.js"></script>
    <script type="text/javascript" src="http://knockoutjs.com/js/knockout-1.2.1.js"></script>
</head>
<body>
    <script type="text/javascript">
        var Page = Page || {};
        Page.Utility = Page.Utility || {};
        Page.Utility.Registration = Page.Utility.Registration || {};

//获取密码强度
        Page.Utility.Registration.getPasswordLevel =function (password) {
            if (password ==null|| password =='')
                return0;

if (password.length <=4)
                return0; //密码太短

var Modes =0;
            for (i =0; i < password.length; i++) {
                Modes |= CharMode(password.charCodeAt(i));
            }
            return bitTotal(Modes);

//CharMode函数 
function CharMode(iN) {
                if (iN >=48&& iN <=57) //数字
return1;
                if (iN >=65&& iN <=90) //大写字母
return2;
                if (iN >=97&& iN <=122) //小写
return4;
                else
                    return8; //特殊字符 
            }

//bitTotal函数
function bitTotal(num) {
                modes =0;
                for (i =0; i <4; i++) {
                    if (num &1) modes++;
                    num >>>=1;
                }
                return modes;
            }
        };

var viewModel = {
            Password: ko.observable(""),
            Ocolor: "#eeeeee"
        };

viewModel.PasswordLevel = ko.dependentObservable(function () {
            return Page.Utility.Registration.getPasswordLevel(this.Password());
        }, viewModel);

viewModel.Lcolor = ko.dependentObservable(function () {
            //根据密码强度判断第一个格显示的背景色
returnthis.PasswordLevel() ==0?this.Ocolor : (this.PasswordLevel() ==1?"#FF0000" : (this.PasswordLevel() ==2?"#FF9900" : "#33CC00"))
        }, viewModel);

viewModel.Mcolor = ko.dependentObservable(function () {
            //根据密码强度判断第二个格显示的背景色
returnthis.PasswordLevel() <2?this.Ocolor : (this.PasswordLevel() ==2?"#FF9900" : "#33CC00")
        }, viewModel);

viewModel.Hcolor = ko.dependentObservable(function () {
            //根据密码强度判断第二个格显示的背景色
returnthis.PasswordLevel() <3?this.Ocolor : "#33CC00"
        }, viewModel);

$((function () {
            ko.applyBindings(viewModel);
        }));

</script>
    <form name="form1" action="">
    输入密码:<input type="text" size="10" data-bind="value:Password, valueUpdate: 'afterkeydown'">
    <br>
    密码强度:
    <table width="217" border="1" cellspacing="0" cellpadding="1" bordercolor="#cccccc"
        height="23" style='display: inline'>
        <tr align="center" bgcolor="#eeeeee">
            <td width="50" id="strength_L" data-bind="style: { backgroundColor: Lcolor }">
                弱
            </td>
            <td width="50" id="strength_M" data-bind="style: { backgroundColor: Mcolor }">
                中
            </td>
            <td width="50" id="strength_H" data-bind="style: { backgroundColor: Hcolor }">
                强
            </td>
        </tr>
    </table>
    </form>
</body>
</html>
```

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