Javascript [Electronic resources] : The Definitive Guide (4th Edition) نسخه متنی

Availability

DOM Level 2 Core; in DOM Level 1, defined by HTMLDocument

Synopsis

Element getElementById(String elementId);

Arguments

elementId

The value of the id attribute of the desired
element.

Returns

The Element node that represents the document element with the
specified id attribute, or null
if no such element is found.

Description

This method searches the document for an Element node with an
id attribute whose value is
elementId, and returns that Element. If no
such Element is found, it returns null. The value
of the id attribute is intended to be unique
within a document, and if this method finds more than one Element
with the specified elementId, it may
return one at random or it may return null.

In HTML documents, this method always searches for attributes named
id. In XML documents, however, it searches for any
attribute whose

type is id,
regardless of what the attribute name is. If XML attribute types are
not known (because, for example, the XML parser could not locate the
document's DTD), this method always returns
null.

This is an important and commonly used method since it provides a
simple way to obtain the Element object that represents a specific
document element. Note that it provides functionality similar to the
nonstandard document.all[] array defined by
Internet Explorer 4 and later. Finally, note that the name of this
method ends with "Id", not with "ID"; be
careful not to misspell it.

See Also

Document.getElementsByTagName( ), Element.getElementsByTagName( ),
HTMLDocument.getElementsByName( )