1. 策略模式

策略模式定义一系列的算法，把它们封装起来，并且可以互相替换。

var strategies = {

      isNonEmpty: function(value,errMsg){

             if(value === ''){

                    return errMsg;

             }

      },

      minLength:function(value,length,errMsg){

             if(value.length < length){

                    return errMsg;

             }

      }

}

var validator = function(){

      this.cache = [];

}

validator.prototype.add = function(dom,rule,errMsg){

      var array = rule.split(':');

      this.cache.push(function(){

             var strategy = array.shift();

             array.unshift(dom.value);

             array.push(errMsg);

             return strategies[strategy].apply(dom, array);

      });

}

validator.prototype.validate = function(){

      for(var i =0,validatorFunc;validatorFunc=this.cache[i++];){

             var msg = validatorFunc();

             if(msg){

                    return msg;

             }

      }

}

validator.add(form.name,'isNonEmpty','用户名不能为空');

validator.add(form.name,'minLength:10','用户名不能为空');

validator.validate();