[Javascript] 如何在客户端验证表单被改变

Form中的每个对象都保留了初始值，所以可以在提交表单时，遍历Form中对象，

检查对象当前的值与初始值是否一致，就判断出了表单是否被修改了。

示例代码

1function IsFormChanged()

2{

3 var isChanged = false;

4 var form = document.forms[0];

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

6 {

7 var element = form.elements[i];

8 var type = element.type;

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

10 {

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

12 {

13 isChanged = true;

14 break;

15 }

16 }

17 else if (type == "radio" || type == "checkbox")

18 {

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

20 {

21 isChanged = true;

22 break;

23 }

24 }

25 else if (type == "select-one")

26 {

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

28 {

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

30 {

31 isChanged = true;

32 break;

33 }

34 }

35 }

36 else

37 {

38 //

39 }

40 }

41

42 return isChanged;

43}