fetchHeaders.ts

import * as https from 'https';

async function fetchHeaders( url: string ) {
	return new Promise( ( resolve, reject ) => {
		https.get( url, response => {
			resolve( response.headers );
		} );
	} );
}

async function test() {
	// Runs one-by-one
	var wpcomHeaders = await fetchHeaders( 'https://wordpress.com' );
	console.log( wpcomHeaders );

	var googleHeaders = await fetchHeaders( 'https://google.com/' );
	console.log( googleHeaders );

	// Runs in parallel
	var headers = await Promise.all( [
		fetchHeaders( 'https://wordpress.com' ),
		fetchHeaders( 'https://google.com/' ),
	] );

	console.log( headers );
}

test();