JQuery-Form表单中默认值的改变

云海梦尘 2011-08-18

最近修改一个js函数,却发现自己需要学习的还很多

函数的主要目的是想知道form表单中的值有没有被改变,原来的函数采用的是if…else/if结构,在这里,我还是把代码贴出来吧:

//函数;

function IsFormChanged(name) {

       var isChanged = false;

//     var form = document.getElementById(name);

       var form = document.forms[name];

       for (var i = 0; i < form.elements.length; i++) {

              var element = form.elements[i];

              var type = element.type;

              if (type == "text" || type == "hidden" || type == "textarea" || type == "button") {

                     if (element.value != element.defaultValue) {

                            isChanged = true;

                            alert("1");

                            break;

                     }

              } else if (type == "radio" || type == "checkbox") {

                     if (element.checked != element.defaultChecked) {

                            isChanged = true;

                            alert("2");

                            break;

                     }

              } else if (type == "select-one"|| type == "select-multiple") {

                     for (var j = 0; j < element.options.length; j++) {

                            if (element.options[j].selected != element.options[j].defaultSelected) {

                                   isChanged = true;

                                   alert("3");

                                   break;

                            }

                     }

              } else {

                     // etc...

              }     

       }   

       alert( isChanged?"你改变了表单的默认值":"表单的值没有改变");

       return isChanged;

}

       这个函数思路很清晰了,但是,我准备采用另外一个方式来重写它,我采用的是switch,于是,一开始,我把if…else/if都改成switch,可是,发现不能验证,后来,我发现了:for循环中使用switch,然后用break的话,退出来的是switch结构,循环还要继续的,而我需要的是直接退回for循环。上网找了一些解决办法,最后发现把switch部分的分离出来单独写成一个函数比较好,但是,考虑到这个函数最终只会在一个函数中使用,就是我们的判断form表单默认值的函数,而且,由于项目开发的需要,我把一些公用的函数都封装起来,所以,最后我把函数改写成了如下的形式:

       var Form={

       IsFormChanged:function(id){

       /*IsFormChangedCase这个函数我本来是放在外面的,和IsFormChanged的级别是一样的,但是现在只有IsFormChanged这个函数使用这个,其原因是因为switch和for中都是用break的缘故,所以,我最终把这个函数作为IsFormChanged函数的一个变量来使用。

       */

              var IsFormChangedCase=function(element){

              var isChanged = false;

              switch(element.type){

                     case "text":

                     case "hidden":

                     case "textarea":

                     case "button":

                            if(element.value != element.defaultValue)

                                   isChanged= true;

                            break;

                     case "radio":

                     case "checkbox":

                            if(element.checked != element.defaultChecked)

                                   isChanged= true;

                            break;

                     case "select-one":

                     case "select-multiple":

                            for (var j = 0; j < element.options.length; j++){

                                   if(element.options[j].selected != element.options[j].defaultSelected){

                                          isChanged= true;

                                          break;

                                   }

                            }

                            break;

                     }

                     return isChanged;  

              };

              var str=false;

              var form = document.getElementById(id);

              for (var i = 0; i < form.elements.length; i++){

                     var element = form.elements[i];

                     if(IsFormChangedCase(element)){

                            str=true;

                            break;

                     }

              }

              return str;      

       }

}

//这个只是测试函数

function test()

{

       var ret=Form.IsFormChanged("frm2");

       alert( ret?"你改变了表单的默认值":"表单的值没有改变");

       return ret;

}

 

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