HTMLCollection

HTMLCollection interface represents a generic collection (array-like object similar to arguments ) of elements (in document order) and offers methods and properties for selecting from the list.

注意: This interface is called HTMLCollection for historical reasons (before the modern DOM, collections implementing this interface could only have HTML elements as their items).

An HTMLCollection in the HTML DOM is live; it is automatically updated when the underlying document is changed.

特性

HTMLCollection.length 只读
Returns the number of items in the collection.

方法

HTMLCollection.item()
Returns the specific node at the given zero-based index into the list. Returns null index 超出范围。
An alternative to accessing collection[ i ] (which instead returns undefined when i is out-of-bounds). This is mostly useful for non-JavaScript DOM implementations.
HTMLCollection.namedItem()
Returns the specific node whose ID or, as a fallback, name matches the string specified by name . Matching by name is only done as a last resort, only in HTML, and only if the referenced element supports the name attribute. Returns null if no node exists by the given name.
An alternative to accessing collection[ name ] (which instead returns undefined when name does not exist). This is mostly useful for non-JavaScript DOM implementations.

Usage in JavaScript

HTMLCollection also exposes its members directly as properties by both name and index. HTML IDs may contain : and . as valid characters, which would necessitate using bracket notation for property access. Currently HTMLCollections does not recognize purely numeric IDs, which would cause conflict with the array-style access, though HTML5 does permit these.

For example, assuming there is one <form> element in the document and its id is myForm :

var elem1, elem2;
// document.forms is an HTMLCollection
elem1 = document.forms[0];
elem2 = document.forms.item(0);
alert(elem1 === elem2); // shows: "true"
elem1 = document.forms.myForm;
elem2 = document.forms.namedItem("myForm");
alert(elem1 === elem2); // shows: "true"
elem1 = document.forms["named.item.with.periods"];
					

规范

规范 状态 Comment
DOM
The definition of 'HTMLCollection' in that specification.
实时标准

浏览器兼容性

更新 GitHub 上的兼容性数据
Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
HTMLCollection Chrome 1 Edge 12 Firefox 1 IE 8 Opera 8 Safari 4 WebView Android 1 Chrome Android 18 Firefox Android 4 Opera Android 10.1 Safari iOS 3.2 Samsung Internet Android 1.0
item Chrome Yes Edge 12 Firefox Yes IE ? Opera Yes Safari Yes WebView Android Yes Chrome Android Yes Firefox Android Yes Opera Android Yes Safari iOS Yes Samsung Internet Android Yes
length Chrome Yes Edge 12 Firefox Yes IE ? Opera Yes Safari Yes WebView Android Yes Chrome Android Yes Firefox Android Yes Opera Android Yes Safari iOS Yes Samsung Internet Android Yes
namedItem Chrome Yes Edge 12 Firefox Yes IE Yes Opera Yes Safari Yes WebView Android Yes Chrome Android Yes Firefox Android Yes Opera Android Yes Safari iOS Yes Samsung Internet Android Yes

图例

完整支持
完整支持
兼容性未知
兼容性未知

另请参阅