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Highlight

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The Highlight interface of the CSS Custom Highlight API is used to represent a collection of AbstractRange instances to be styled using the API.

To style arbitrary ranges in a page, instantiate a new Highlight object, add one or more AbstractRange objects to it, and register it using the HighlightRegistry.

A Highlight instance is a Set-like object that can hold one or more AbstractRange objects.

Constructor

  • Highlight()
    • : Returns a newly created Highlight object.

Instance properties

The Highlight interface doesn’t inherit any properties.

  • priority
    • : A number that indicates the priority of this Highlight object. When multiple highlights overlap, the browser uses this priority to decide how to style the overlapping parts.
  • size Read only
    • : Returns the number of ranges in the Highlight object.
  • type
    • : An enumerated String used to specify the semantic meaning of the highlight. This allows assistive technologies to include this meaning when exposing the highlight to users.

Instance methods

The Highlight interface doesn’t inherit any methods.

  • add()
    • : Add a new range to this highlight.
  • clear()
    • : Remove all ranges from this highlight.
  • delete()
    • : Remove a range from this highlight.
  • entries()
    • : Returns a new iterator object that contains each range in the highlight object, in insertion order.
  • forEach()
    • : Calls the given callback once for each range in the highlight object, in insertion order.
  • has()
    • : Returns a boolean asserting whether a range is present the highlight object or not.
  • keys()
  • values()
    • : Returns a new iterator object that yields the ranges in the highlight object in insertion order.

Examples

The following example demonstrates how specific parts of a block of text can be highlighted.

<p class="foo">Lorem ipsum dolor sit amet consectetur adipisicing elit. Exercitationem
  sapiente non eum facere? Nam rem hic culpa, ipsa rerum ab itaque consectetur
  molestiae dolores vitae! Quo ex explicabo tempore? Tenetur.</p>

This JavaScript code creates ranges, instantiates a new Highlight object for them, and registers it to be styled on the page:

const parentNode = document.querySelector(".foo");
const textNode = parentNode.firstChild;

// Create a couple of ranges.
const range1 = new Range();
range1.setStart(textNode, 6);
range1.setEnd(textNode, 21);

const range2 = new Range();
range2.setStart(textNode, 57);
range2.setEnd(textNode, 71);

// Create a custom highlight for these ranges.
const highlight = new Highlight(range1, range2);

// Register the ranges in the HighlightRegistry.
CSS.highlights.set("my-custom-highlight", highlight);

The following CSS code snippet demonstrates how to style the registered custom highlight by using the ::highlight pseudo-element:

::highlight(my-custom-highlight) {
  background-color: peachpuff;
}

Result

Interactive exampleOpen the canonical MDN source to run this embedded demo.

Specifications

SpecificationsStandards references are available on the canonical MDN page.

Browser compatibility

Browser compatibilityCompatibility data is available on the canonical MDN page.

See also