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本文實例講述了JavaScript判斷用戶是否對表單進行了修改的方法。分享給大家供大家參考。具體分析如下：

這段JS代碼可以判斷出用戶是否對表單內容進行了修改，如果修改了表單，並退出浏覽器，則會提醒用戶是否要保存表單的內容，是非常有用的代碼。

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：當退出浏覽器是，如果用戶修改了表單，則提醒用戶是否要保存

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.";
 }
};

下面是一個完整的范例代碼
復制代碼 代碼如下: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>

希望本文所述對大家的javascript程序設計有所幫助。