JavaScript判断用户是否对表单进行了修改的方法

2019-11-20 12:54:05

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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

复制代码代码如下:

Click on below button. Now change some values in form and click the button again.
<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>