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

HighlightRegistry is a Map-like object, so this is similar to using Map.forEach().

callback

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

highlight

The current highlight.

name

The highlight name.

registry

The registry 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 logAllHighlights(highlight, name) {
  console.log(`Highlight ${name} exists in the registry`, highlight);
}

const customHighlight1 = new Highlight();
const customHighlight2 = new Highlight();
const customHighlight3 = new Highlight();

CSS.highlights.set("custom-highlight-1", customHighlight1);
CSS.highlights.set("custom-highlight-2", customHighlight2);
CSS.highlights.set("custom-highlight-3", customHighlight3);

CSS.highlights.forEach(logAllHighlights);

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