设置表单的默认值、检测表单是否变更

通过动态加载表单内容，要求检测加载之后有没有变更过，可以通过defaultValue或者defaultSelected、defaultChecked属性来完成

首先，加载完成后设置默认值为当前状态的值：

//设置当前值为表单默认值
function setDefault(element) {
if (typeof (element) == "string") {
element = document.getElementById(element);
if (!element) { return null; }
}
var type = element.type;
if (type == "checkbox" || type == "radio") {
element.defaultChecked = element.checked;
}
else if (type == "hidden" || type == "password" || type == "text" || type == "textarea") {
element.defaultValue = element.value;
}
else if (type == "select-one" || type == "select-multiple") {
for (var j = 0; j < element.options.length; j++) {
element.options[j].defaultSelected = element.options[j].selected;
}
}
var childs = element.childNodes;
for (var i = 0; i < childs.length; i++) {
setDefault(childs[i]);
}
}

检测代码：

//判断表单是否改变过
function formIsDirty(form) {
if (typeof (form) == "string") {
form = document.getElementById(form);
if (!form) { return null;}
}
for (var i = 0; i < form.elements.length; i++) {
var element = form.elements[i];
var type = element.type;
if (type == "checkbox" || type == "radio") {
if (element.checked != element.defaultChecked) {
return true;
}
}
else if (type == "hidden" || type == "password" || type == "text" || type == "textarea") {
if (element.value != element.defaultValue) {
return true;
}
}
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) {
return true;
}
}
}
}
return false;
}