Promise/async/await for calling asynchronous API like synchronous

async-await-02.js

'use strict';

const start_time = Date.now();
function timestamp_log(message) {
  const duration = Date.now() - start_time;
  console.log(`[${duration}]: ${message}`);
}

timestamp_log('script start');

function callback_at_late(param, resolve, reject) {
  timestamp_log('callback_at_late start');
  timestamp_log(`callback_at_late param: ${param}`);
  timestamp_log('callback_at_late end');
  resolve(`callback_at_late(${param})`);
  return;
}

function background_procedure(callback, param) {
  timestamp_log('background_procedure start');
  const background_promise = new Promise(function(background_resolve, background_reject) {
    setTimeout(callback, 3000, param, background_resolve, background_reject);
  });
  timestamp_log('background_procedure end');
  return background_promise;
}

function foreground_procedure_01(param) {
  timestamp_log('foreground_procedure_01 start');
  timestamp_log(`foreground_procedure_01 param: ${param}`);
  timestamp_log('foreground_procedure_01 end');
}

function foreground_procedure_02(param) {
  timestamp_log('foreground_procedure_02 start');
  timestamp_log(`foreground_procedure_02 param: ${param}`);
  timestamp_log('foreground_procedure_02 end');
}

function foreground_procedure_03(param) {
  timestamp_log('foreground_procedure_03 start');
  timestamp_log(`foreground_procedure_03 param: ${param}`);
  timestamp_log('foreground_procedure_03 end');
}

function foreground_procedure_04(param) {
  timestamp_log('foreground_procedure_04 start');
  timestamp_log(`foreground_procedure_04 param: ${param}`);
  timestamp_log('foreground_procedure_04 end');
}

async function subroutine() {
  timestamp_log('subroutine start');
  const background_result = await background_procedure(callback_at_late, 'BACKGROUND');
  timestamp_log('background_promise');
  foreground_procedure_01(background_result);
  foreground_procedure_02(background_result);
  timestamp_log('subroutine end');
  return `subroutine(${background_result})`;
}

async function main() {
  timestamp_log('main start');
  const subroutine_result = await subroutine();
  foreground_procedure_03(subroutine_result);
  foreground_procedure_04(subroutine_result);
  timestamp_log('main end');
}

main();

timestamp_log('script end');