前言
密码，如果设置的太简单，很容易就被攻破，所以很多网站将密码设置的要求设置的挺严格，一般是字母、数字、字符3选2，区分大小写。对于设置得太简单的密码，予以错误提示。或者予以密码等级（低中高）显示，让用户设置高级密码。那如何利用JS实现呢？
代码
链接：/xuanfeng/a44f20cb4569d5b4cd5e
使用
普通使用
使用语法：passwordLevel(string)
验证规则：数字、大写字母、小写字母、特殊字符
函数结果：返回密码中包含的规则数
运行例子：
结合jquery.validate.js使用
<script type="text/javascript">function checkForm(form){if(form.username.value == "") {alert("Error: Username cannot be blank!");form.username.focus();return false;}re = /^\w+$/;if(!re.test(form.username.value)) {alert("Error: Username must contain only letters, numbers and underscores!");form.username.focus();return false;}if(form.pwd1.value != "" && form.pwd1.value == form.pwd2.value) {if(form.pwd1.value.length < 6) {alert("Error: Password must contain at least six characters!");form.pwd1.focus();return false;}if(form.pwd1.value == form.username.value) {alert("Error: Password must be different from Username!");form.pwd1.focus();return false;}re = /[0-9]/;if(!re.test(form.pwd1.value)) {alert("Error: password must contain at least one number (0-9)!");form.pwd1.focus();return false;}re = /[a-z]/;if(!re.test(form.pwd1.value)) {alert("Error: password must contain at least one lowercase letter (a-z)!");form.pwd1.focus();return false;}re = /[A-Z]/;if(!re.test(form.pwd1.value)) {alert("Error: password must contain at least one uppercase letter (A-Z)!");form.pwd1.focus();return false;}} else {alert("Error: Please check that you've entered and confirmed your password!");form.pwd1.focus();return false;}alert("You entered a valid password: " + form.pwd1.value);return true;}</script>
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