Document: getElementsByTagName() method
The getElementsByTagName
method of
Document
interface returns an
HTMLCollection
of elements with the given tag name.
The complete
document is searched, including the root node. The returned HTMLCollection
is live, meaning that it updates itself automatically to stay in sync with the DOM tree
without having to call document.getElementsByTagName()
again.
Syntax
getElementsByTagName(name)
Parameters
name
-
A string representing the name of the elements. The special string
*
represents all elements.
Return value
A live HTMLCollection
of found elements in the order they appear in the tree.
Examples
In the following example, getElementsByTagName()
starts from a particular
parent element and searches top-down recursively through the DOM from that parent
element, building a collection of all descendant elements which match the tag
name
parameter. This demonstrates both
document.getElementsByTagName()
and the functionally identical
Element.getElementsByTagName()
, which starts the search at a specific
element within the DOM tree.
Clicking the buttons uses getElementsByTagName()
to count the descendant
paragraph elements of a particular parent (either the document itself or one of two
nested <div>
elements).
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>getElementsByTagName example</title>
<script>
function getAllParaElems() {
const allParas = document.getElementsByTagName("p");
const num = allParas.length;
alert(`There are ${num} paragraph in this document`);
}
function div1ParaElems() {
const div1 = document.getElementById("div1");
const div1Paras = div1.getElementsByTagName("p");
const num = div1Paras.length;
alert(`There are ${num} paragraph in #div1`);
}
function div2ParaElems() {
const div2 = document.getElementById("div2");
const div2Paras = div2.getElementsByTagName("p");
const num = div2Paras.length;
alert(`There are ${num} paragraph in #div2`);
}
</script>
</head>
<body style="border: solid green 3px">
<p>Some outer text</p>
<p>Some outer text</p>
<div id="div1" style="border: solid blue 3px">
<p>Some div1 text</p>
<p>Some div1 text</p>
<p>Some div1 text</p>
<div id="div2" style="border: solid red 3px">
<p>Some div2 text</p>
<p>Some div2 text</p>
</div>
</div>
<p>Some outer text</p>
<p>Some outer text</p>
<button onclick="getAllParaElems();">
Show all p elements in document
</button>
<br />
<button onclick="div1ParaElems();">
Show all p elements in div1 element
</button>
<br />
<button onclick="div2ParaElems();">
Show all p elements in div2 element
</button>
</body>
</html>
Notes
When called on an HTML document, getElementsByTagName()
lower-cases its
argument before proceeding. This is undesirable when trying to match camel case SVG
elements in a subtree in an HTML document.
document.getElementsByTagNameNS()
is useful in that case. See also
Firefox bug 499656.
document.getElementsByTagName()
is similar to
Element.getElementsByTagName()
, except that its search encompasses the
whole document.
Specifications
Specification |
---|
DOM Standard # ref-for-dom-document-getelementsbytagname① |
Browser compatibility
BCD tables only load in the browser
See also
Element.getElementsByTagName()
-
document.getElementById()
to return a reference to an element by itsid
-
document.getElementsByName()
to return a reference to an element by itsname
-
document.querySelector()
for powerful selectors via queries like'div.myclass'