本文实例讲述了JavaScript判断用户是否对表单进行了修改的方法。分享给大家供大家参考。具体分析如下：
这段JS代码可以判断出用户是否对表单内容进行了修改，如果修改了表单，并退出浏览器，则会提醒用户是否要保存表单的内容，是非常有用的代码。
function formIsDirty(form) {
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;
}使用示例：当退出浏览器是，如果用户修改了表单，则提醒用户是否要保存
window.onbeforeunload = function(e) {
e = e || window.event;
if (formIsDirty(document.forms["someForm"])) {
// For IE and Firefox
if (e) {
e.returnValue = "You have unsaved changes.";
}
// For Safari
return "You have unsaved changes.";
}
};下面是一个完整的范例代码
<form name="fooForm">
<input type="text" name="t"><br>
<input type="text" name="2" value="default"><br>
<select name="some">
<option value="fooo" selected="">foo</option>
<option value="bar">bar</option>
</select><br>
</form>
<button onclick="alert(formIsDirty(document.fooForm))">Click to check if Form is Dirty</button>
<br>
<script>
function formIsDirty(form) {
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;
}
</script>
希望本文所述对大家的javascript程序设计有所帮助。