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.

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 DOMException

Thrown if 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:

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

This example uses the :scope pseudo-class to retrieve direct children of the parentElement element.

HTML

<div>
  <h6>Page Title</h6>
  <div id="parent">
    <span>Love is Kind.</span>
    <span>
      <span>Love is Patient.</span>
    </span>
    <span>
      <span>Love is Selfless.</span>
    </span>
  </div>
</div>

CSS

span {
  display: block;
  margin-bottom: 5px;
}
.red span {
  background-color: red;
  padding: 5px;
}

JavaScript

const parentElement = document.querySelector("#parent");
let allChildren = parentElement.querySelectorAll(":scope > span");
allChildren.forEach((item) => item.classList.add("red"));

Result

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

const 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).

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

• 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()
• Other methods that take selectors: element.closest() and element.matches().