Element: beforematch event

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("beforematch", (event) => {});

onbeforematch = (event) => {};

A generic Event.

The HTML hidden attribute accepts a value until-found: when this value is specified, the element is hidden but its content will be accessible to the browser's "find in page" feature or to fragment navigation. When these features cause a scroll to an element in a "hidden until found" subtree, the browser will:

• fire a beforematch event on the hidden element
• remove the hidden attribute from the element
• scroll to the element

In this example we have:

• Two <div> elements. The first is not hidden, while the second has hidden="until-found"and id="until-found-box" attributes.
• A link whose target is the "until-found-box" fragment.

We also have some JavaScript that listens for the beforematch event firing on the hidden until found element. The event handler changes the text content of the box.

HTML

<a href="#until-found-box">Go to hidden content</a>

<div>I'm not hidden</div>
<div id="until-found-box" hidden="until-found">Hidden until found</div>

<button id="reset">Reset</button>

CSS

div {
  height: 40px;
  width: 300px;
  border: 5px dashed black;
  margin: 1rem 0;
  padding: 1rem;
  font-size: 2rem;
}

#until-found-box {
  scroll-margin-top: 200px;
}

JavaScript

const untilFound = document.querySelector("#until-found-box");
untilFound.addEventListener(
  "beforematch",
  () => (untilFound.textContent = "I've been revealed!")
);

document.querySelector("#reset").addEventListener("click", () => {
  document.location.hash = "";
  document.location.reload();
});

Result

Clicking the "Go to hidden content" button navigates to the hidden-until-found element. The beforematch event fires, the text content is updated, and then the element's content is displayed.

To run the example again, click "Reload".

If your browser does not support the "until-found" enumerated value of the hidden attribute, the second <div> will be hidden (as hidden was boolean prior to the addition of the until-found value).

• The HTML hidden attribute