Add a `by.marker` locator to Protractor to match elements marked with an "e2e" attribute

by_marker.d.ts

import {Locator} from "protractor/built/locators";

declare module "protractor/built/locators" {
	export interface ProtractorBy {
		marker(marker: string, parentElement?: Node): Locator;
	}
}

protractor.conf.ts

by.addLocator("marker", (marker: string, parentElement?: Element) => {
	const scope = parentElement || document;
	const matches = scope.querySelectorAll(`[e2e="${marker}"]`);
	if (matches.length === 0) {
		return null;
	} else if (matches.length === 1) {
		return matches[0];
	}
	return matches;
});