The forEach() method of the Highlight interface executes a provided function once for each Range object in the Highlight object, in insertion order.

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

callback

Function to execute for each Range object, taking three arguments:

range, key

The current Range object being processed in the Highlight. As there are no keys in Highlight, the range is passed for both arguments.

highlight

The Highlight object which forEach() was called upon.

thisArg

Value to use as this when executing callbackFn.

None (undefined).

The code snippet below shows how create a new highlight with two ranges, and then log the ranges by using the forEach() method:

function logRanges(range, key, highlight) {
  console.log(`Highlight object ${highlight} contains range ${range}`);
}

const text = new Text("Time is an illusion. Lunchtime doubly so.");

const range1 = document.createRange();
range1.setStart(text, 0);
range1.setEnd(text, 4);

const range2 = document.createRange();
range2.setStart(text, 21);
range2.setEnd(text, 30);

const myHighlight = new Highlight();
myHighlight.add(range1);
myHighlight.add(range2);

myHighlight.forEach(logRanges);

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