files/en-us/web/api/documentfragment/queryselector/index.md
{{ApiRef("DOM")}}
The DocumentFragment.querySelector() method returns the
first element, or null if no matches are found, within the
{{domxref("DocumentFragment")}} (using depth-first pre-order traversal of the
document's nodes) that matches the specified group of selectors.
If the selector matches an ID and this ID is erroneously used several times in the document, it returns the first matching element.
If the selectors specified in parameter are invalid a {{domxref("DOMException")}} with
a SYNTAX_ERR value is raised.
querySelector(selectors)
selectors
An {{domxref("Element")}} object representing the first element in the document
that matches the specified set of CSS selectors, or null is returned if there are no matches.
In this basic example, the first element in the {{domxref("DocumentFragment")}} with
the class myclass is returned:
const el = documentfragment.querySelector(".myclass");
The string argument pass to querySelector must follow the CSS syntax. To
match ID or selectors that do not follow the CSS syntax (by using semicolon or space
inappropriately for example), it's mandatory to escape the wrong character with a
double back slash:
<div id="foo\bar"></div>
<div id="foo:bar"></div>
document.querySelector("#foo\bar"); // Does not match anything
document.querySelector("#foo\\\\bar"); // Match the first div
document.querySelector("#foo:bar"); // Does not match anything
document.querySelector("#foo\\:bar"); // Match the second div
{{Specifications}}
{{Compat}}