Highlight

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

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

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

A single Highlight object can hold one or more Range objects and behaves like a Set.

Constructor

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

Instance properties

The Highlight interface doesn't inherit any properties.

Highlight.priority Experimental: 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.
Highlight.size Read only Experimental: Returns the number of ranges in the Highlight object.
Highlight.type Experimental: 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.

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

Examples

The following example demonstrates how to create ranges, instantiate a new Highlight object for them, and register it to be styled on the page:

const parentNode = document.getElementById("foo");

// Create a couple of ranges.
const range1 = new Range();
range1.setStart(parentNode, 10);
range1.setEnd(parentNode, 20);

const range2 = new Range();
range2.setStart(parentNode, 40);
range2.setEnd(parentNode, 60);

// 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;
}

Specifications

Specification
CSS Custom Highlight API Module Level 1 # highlight

Browser compatibility

BCD tables only load in the browser