var strategies={
                    isNonEmpty:function(value,errorMsg){
                        if(value===""){
                            return errorMsg;
                        }
                    },
                    minLength:function(value,length,errorMsg){
                        if(value.length<length){
                            return errorMsg;
                        }
                    },
                    isMoblie:function(value,errorMsg){
                        if(!/(^1[3|5|8][0-9]$)/.test(value)){
                            return errorMsg;
                        }
                    }
                }

                var Validator=function(){this.cache=[];};

                Validator.prototype.add=function(dom,rule,errorMsg){
                    var ary=rule.split(":");
                    this.cache.push(function(){
                        var strategy=ary.shift();
                        ary.unshift(dom.value);
                        ary.push(errorMsg);
                        //1、这下面的return返回的是什么意思
                        //2、strategies这个对象下没有这个[strategy]属性吧，
                        return strategies[strategy].apply(dom,ary);
                    });
                };

                Validator.prototype.start=function(){
                    //3、这个循环validatorFunc是变量他里面好像也没用到他吧,
                    //   这个validatorFunc变量是下面这个validatorFunc()吗？？
                    //   下面的 validatorFunc()是调用的方法来的吧??
                    for(var i=0,validatorFunc;validatorFunc=this.cache[i++];){
                        var msg=validatorFunc();
                        if(msg){
                            return msg;
                        }
                    }
                };

                var validataFunc=function(){
                    var validator=new Validator();
                    validator.add(registerForm.userName,"isNonEmpty","用户名不能为空");
                    validator.add(registerForm.password,"minLength:6","密码长度不能小于6位");
                    validator.add(registerForm.phoneNumber,"isMobile","手机号码格式不正确");
                    var errorMsg=validator.start();
                    return errorMsg;
                }

                var registerForm=document.getElementById("registerForm");
                registerForm.onsubmit=function(){
                    var errorMsg=validataFunc();
                    if(errorMsg){
                        alert(errorMsg);
                        return false;
                    }
                }

        ----html-----    
        <form action="http://www.xxx.com" id="registerForm" method="post">
        请输入用户名：<input type="text" name="userName" /><br/>
        请输入密码：<input type="text" name="password" /><br/>
        请输入手机号码：<input type="text" name="phoneNumber" /><br/>
        <button>提交</button>