Element.querySelector()

Returns the first element that is a descendant of the element on which it is invoked that matches the specified group of selectors.

element = baseElement.querySelector(selectors);

selectors

A group of selectors to match the descendant elements of the Element baseElement against; this must be valid CSS syntax, or a SyntaxError exception will occur. The first element found which matches this group of selectors is returned.

The first descendant element of baseElement which matches the specified group of selectors. The entire hierarchy of elements is considered when matching, including those outside the set of elements including baseElement and its descendants; in other words, selectors is first applied to the whole document, not the baseElement, to generate an initial list of potential elements. The resulting elements are then examined to see if they are descendants of baseElement. The first match of those remaining elements is returned by the querySelector() method.

If no matches are found, the returned value is null.

SyntaxError

The specified selectors are invalid.

Let's consider a few examples.

In this first example, the first <style> element which either has no type or has type "text/css" in the HTML document body is returned:

var el = document.body.querySelector("style[type='text/css'], style:not([type])");

The next example, below, demonstrates that the hierarchy of the entire document is considered when applying selectors, so that levels which are outside the specified baseElement are still considered when locating matches.

HTML

<div>
  <h5>Original content</h5>
  <p>
    inside paragraph
    <span>inside span</span>
    inside paragraph
  </p>
</div>
<div>
  <h5>Output</h5>
  <div id="output"></div>
</div>

JavaScript

var baseElement = document.querySelector("p");
document.getElementById("output").innerHTML =
         (baseElement.querySelector("div span").innerHTML);

Result

The result looks like this:

Notice how the "div span" selector still matches the <span> element, even though the baseElement excludes the div element which is part of the specified selector.

The :scope pseudo-class restores the expected behavior, only matching selectors on descendants of the baseElement.

See Document.querySelector() for additional examples of the proper format for the selectors.

[1] querySelector() is supported in IE8, but only for CSS 2.1 selectors.
[2] in IE8 and iE9 document must be in HTML5 mode (HTML5 doctype declaration present)

• element.querySelectorAll()
• document.querySelector()
• document.querySelectorAll()
• Code snippets for querySelector