Element.querySelector() - Web APIs 编辑

The querySelector() method of the Element interface returns the first element that is a descendant of the element on which it is invoked that matches the specified group of selectors.

Syntax

element = baseElement.querySelector(selectors);

Parameters

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.

Return value

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.

Exceptions

SyntaxError

The specified selectors are invalid.

Examples

Let's consider a few examples.

Find a specific element with specific values of an attribute

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 entire hierarchy counts

This example demonstrates that the hierarchy of the entire document is considered when applying selectors, so that levels 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 successfully matches the <span> element, even though the baseElement's child nodes do not include the div element (it is still part of the specified selector).

More examples

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

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Locating DOM elements using selectors
• Attribute selectors in the CSS Guide
• Attribute selectors in the MDN Learning Area
• Element.querySelectorAll()
• Document.querySelector() and Document.querySelectorAll()
• DocumentFragment.querySelector() and DocumentFragment.querySelectorAll()
• ParentNode.querySelector() and ParentNode.querySelectorAll()
• Code snippets for querySelector
• Other methods that take selectors: element.closest() and element.matches().