功能强大的jquery.validate表单验证插件

<script src="jquery.js"></script>
<script src="lib/jquery.validate.min.js"></script>
<script src="lib/jquery.validate.extend.js"></script>

<form action="#" method="post" id="regForm">
  <fieldset>
    <legend>jquery-validate表单校验验证</legend>
    <div class="item">
      <label for="username" class="item-label">用户名:</label>
      <input type="text" id="username" name="username" class="item-text" placeholder="设置用户名"
      autocomplete="off" tip="请输入用户名">
    </div>
    <div class="item">
      <label for="password" class="item-label">密码:</label>
      <input type="password" id="password" name="password" class="item-text" placeholder="设置密码"
      tip="长度为6-16个字符">
    </div>
    <div class="item">
      <label for="password" class="item-label">确认密码:</label>
      <input type="password" name="repassword" class="item-text" placeholder="设置确认密码">
    </div>
    <div class="item">
      <label for="amt" class="item-label">金额:</label>
      <input type="text" id="amt" name="amt" class="item-text" placeholder="交易金额"
      tip="交易金额必须大于0，且最多有两位小数">
    </div>
    <div class="item">
      <input type="submit" value="提交" class="item-submit">
    </div>
  </fieldset>
</form>

/*******************************插件新功能-设置插件validator的默认参数*****************************************/
$.validator.setDefaults({
  /*关闭键盘输入时的实时校验*/
  onkeyup: null,
  /*添加校验成功后的执行函数--修改提示内容，并为正确提示信息添加新的样式(默认是valid)*/
  success: function(label){
    /*label的默认正确样式为valid，需要通过validClass来重置，否则这里添加的其他样式不能被清除*/
    label.text('').addClass('valid');
  },
  /*重写校验元素获得焦点后的执行函数--增加[1.光标移入元素时的帮助提示,2.校验元素的高亮显示]两个功能点*/
  onfocusin: function( element ) {
    this.lastActive = element;
    
    /*1.帮助提示功能*/
    this.addWrapper(this.errorsFor(element)).hide();
    var tip = $(element).attr('tip');
    if(tip && $(element).parent().children(".tip").length === 0){
      $(element).parent().append("<label class='tip'>" + tip + "</label>");
    }
    
    /*2.校验元素的高亮显示*/
    $(element).addClass('highlight');

    // Hide error label and remove error class on focus if enabled
    if ( this.settings.focusCleanup ) {
      if ( this.settings.unhighlight ) {
        this.settings.unhighlight.call( this, element, this.settings.errorClass, this.settings.validClass );
      }
      this.hideThese( this.errorsFor( element ) );
    }
  },
  /*重写校验元素焦点离开时的执行函数--移除[1.添加的帮助提示,2.校验元素的高亮显示]*/
  onfocusout: function( element ) {
    /*1.帮助提示信息移除*/
    $(element).parent().children(".tip").remove();

    /*2.校验元素高亮样式移除*/
    $(element).removeClass('highlight');
    
    /*3.替换下面注释的原始代码，任何时候光标离开元素都触发校验功能*/
    this.element( element );
    
    /*if ( !this.checkable( element ) && ( element.name in this.submitted || !this.optional( element ) ) ) {
      this.element( element );
    }*/
  }
});

<script>
$(document).ready(function(){
  $("#regForm").validate({
    rules: {
      username:{
        required: true,
        minlength: 2
      },
      password:{
        required: true,
        minlength: 6,
        maxlength: 16
      },
      repassword:{
        required: true,
        equalTo: "#password"
      },
      amt: {
        required: true,
        amtCheck: true
      }
    },
    messages:{
      username:{
        required: "用户名不能为空",
        minlength: "用户名的最小长度为2"
      },
      password:{
        required: "密码不能为空",
        minlength: "密码长度不能少于6个字符",
        maxlength: "密码长度不能超过16个字符"
      },
      repassword:{
        required: "确认密码不能为空",
        equalTo: "确认密码和密码不一致"
      },
      amt: {
        required: "金额不能为空"
      }
    }
  });
});
</script>

body{
  font-family: Microsoft Yahei;
  font-size: 15px;
}

fieldset{  width: 680px;  }

legend{  margin-left: 8px;  }

.item{
  height: 56px;
  line-height: 36px;
  margin: 10px;
}

.item .item-label{
  float: left;
  width: 80px;
  text-align: right;
}

.item-text{
  float: left;
  width: 244px;
  height: 16px;
  padding: 9px 25px 9px 5px;
  margin-left: 10px;
  border: 1px solid #ccc;
  overflow: hidden;
}

.item-select{
  float: left;
  height: 34px;
  border: 1px solid #ccc;
  margin-left: 10px;
  font-size: 14px;
  padding: 6px 0px;
}

.item-submit{
  margin-left: 88px;
}

input.error{
  border: 1px solid #E6594E;
}

input.highlight{
  border: 1px solid #7abd54;
}

label.error,label.tip{
  float: left;
  height: 32px;
  line-height: 32px;
  font-size: 14px;
  text-align: left;
  margin-left: 5px;
  padding-left: 20px;
  color: red;
  background: url('error.png') no-repeat left center;
}

label.tip{
  color: #aaa;
  background: url('tip.png') no-repeat left center;
}

label.valid{
  background: url('valid.png') no-repeat left center;
  width: 32px;
}

/*******************************插件字段校验*****************************************/
$.validator.addMethod(
  "amtCheck",
  function(value, element){
    /*var dotPos = value.indexOf('.');
    return value > 0 && dotPos < 0 && (dotPos > 0 && value.substring(dotPos + 1) <= 2);*/
    
    return value && /^\d*\.?\d{0,2}$/.test(value);
  },
  "金额必须大于0且小数位数不超过2位"
);