jQuery的表单验证插件：validate详解与使用示例

$(document).ready(function() {
    $("#myform").validate({
        rules: {
            firstname: "required",
            lastname: "required",
            username: {
                required: true,
                minlength: 2
            },
            password: {
                required: true,
                minlength: 5
            },
            confirm_password: {
                required: true,
                minlength: 5,
                equalTo: "#password"
            },
            email: {
                required: true,
                email: true
            },
            topic: {
                required: "#newsletter:checked",
                minlength: 2
            },
            agree: "required"
        },
        messages: {
            firstname: "请输入您的名字",
            lastname: "请输入您的姓氏",
            username: {
                required: "请输入用户名",
                minlength: "用户名至少需要 2 个字符"
            },
            password: {
                required: "请输入密码",
                minlength: "密码至少需要 5 个字符"
            },
            confirm_password: {
                required: "请输入确认密码",
                minlength: "确认密码至少需要 5 个字符",
                equalTo: "两次输入密码不一致"
            },
            email: "请输入一个有效的电子邮件地址",
            topic: "请选择至少两个兴趣主题",
            agree: "请接受使用条款。"
        },
        errorElement: "em",
        errorPlacement: function(error, element) {
            // 错误信息放置在输入框的后面
            error.insertAfter(element);
        },
        highlight: function(element, errorClass, validClass) {
            $(element).addClass(errorClass).removeClass(validClass);
        },
        unhighlight: function(element, errorClass, validClass) {
            $(element).removeClass(errorClass).addClass(validClass);
        }
    });
});

这段代码使用jQuery Validate插件来验证一个表单的输入数据是否满足预设的规则。它定义了一些基本的验证规则和错误信息，并指定了错误提示的显示方式。在实际应用中，开发者可以根据具体需求调整规则和错误消息。