HTMLCollection interface represents a generic collection (array-like object) of elements (in document order) and offers methods and properties for selecting from the list.
HTMLCollectionfor historical reasons (before DOM4, collections implementing this interface could only have HTML elements as their items).
HTMLCollection in the HTML DOM is live; it is automatically updated when the underlying document is changed.
- Returns the number of items in the collection.
- Returns the specific node at the given zero-based
indexinto the list. Returns
indexis out of range.
- 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
nullif no node exists by the given name.
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
var elem1, elem2; // document.forms is an HTMLCollection elem1 = document.forms; 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"];
Different browsers behave differently when there are more than one elements matching the string used as an index (or
namedItem's argument). Firefox 8 behaves as specified in DOM 2 and DOM4, returning the first matching element. WebKit browsers and Internet Explorer in this case return another
HTMLCollection and Opera returns a
NodeList of all matching elements.