The has() method of the Highlight interface returns a boolean indicating whether a Range object exists in a Highlight object or not.

Highlight is a Set-like object, so this is similar to using Set.has().

range

The Range object to test for presence in the Highlight object.

Returns true if the specified range exists in the Highlight object; otherwise false.

The code snippet below creates two ranges, and a highlight object that contains one of them. The code then uses the has() method to check whether each range exists in the highlight:

const range1 = new Range();
const range2 = new Range();
const myHighlight = new Highlight(range1);

myHighlight.has(range1); // true
myHighlight.has(range2); // false

• The CSS Custom Highlight API
• CSS Custom Highlight API: The Future of Highlighting Text Ranges on the Web