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• 句法
• 范例
• 规范
• 浏览器兼容性
• 相关话题

MutationObserverInit dictionary's optional attributeOldValue property is used to specify whether or not to record the prior value of the altered attribute in MutationRecord objects denoting attribute value changes.

句法

var options = {
  attributeOldValue: true | false
}
					

值

A Boolean value indicating whether or not the prior value of a changed attribute should be included in the MutationObserver.oldValue property when reporting attribute value changes. If true , oldValue is set accordingly. If false , it is not.

当使用 attributeOldValue , setting the 属性 选项到 true is optional.

范例

In this example, a Mutation Observer is set up to watch for changes to the status and username attributes in any elements contained within a subtree that displays the names of users in a chat room. This lets the code, for example, reflect changes to users' nicknames, or to mark them as away from keyboard (AFK) or offline.

function callback(mutationList) {
  mutationList.forEach(function(mutation) {
    switch(mutation.type) {
      case "attributes":
        notifyUser("Attribute name " + mutation.attributeName +
            " changed to " + mutation.target[mutation.attributeName] +
            " (was " + mutation.oldValue + ")");
        break;
    }
  });
}
var targetNode = document.querySelector("#target");
var observer = new MutationObserver(callback);
observer.observe(targetNode, {
  attributes: true,
  attributeOldValue: true
});
					

callback() function—which will be passed into the observe() method when starting the observer, looks at each item in the list of MutationRecord objects. For any items representing an attribute change (which can be detected by the value of MutationRecord.type being "attributes" ), a function called notifyUser() is used to tell the user the name of the attribute that changed as well as the attribute's new value ( mutation.target[mutation.attributeName] ) and its old value ( mutation.oldValue ).

当 observe() is called, the specified options are 属性 and attributeOldValue , which means that changes to attribute values will be reported, and each mutation record will include the oldValue property specifying the attribute's previous value.

规范

规范	状态	注释
DOM The definition of 'MutationObserverInit.attributeOldValue' in that specification.	实时标准

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
attributeOldValue	Chrome 26 26 18 — 26 Prefixed Prefixed Implemented with the vendor prefix: webkit	Edge 12	Firefox 14 注意事项 14 注意事项 Starting in Firefox 36, attributeOldValue has no default value; previously, its default value was false .	IE 11	Opera 15	Safari 7 7 6 — 7 Prefixed Prefixed Implemented with the vendor prefix: webkit	WebView Android ?	Chrome Android 26 26 18 — 26 Prefixed Prefixed Implemented with the vendor prefix: webkit	Firefox Android 14 注意事项 14 注意事项 Starting in Firefox 36, attributeOldValue has no default value; previously, its default value was false .	Opera Android 14	Safari iOS 7 7 6 — 7 Prefixed Prefixed Implemented with the vendor prefix: webkit	Samsung Internet Android 1.5 1.5 1.0 — 1.5 Prefixed Prefixed Implemented with the vendor prefix: webkit

图例

完整支持

完整支持

兼容性未知 ?

兼容性未知

见实现注意事项。

要求使用供应商前缀或不同名称。

要求使用供应商前缀或不同名称。

元数据

• 最后修改： Mar 18, 2019

相关话题

1. MutationObserverInit
2. 特性

   1. attributeFilter
   2. attributeOldValue
   3. 属性
   4. characterData