setTimeout based on the audioContext timer

override-set-timeout-a.js

function customTimeoutFunction(audioContext) {

  let tasks = [];
  let nextTaskId = 1;

  function now() {
    return audioContext.currentTime * 1000;
  }

  function scheduler() {
    const currentTime = now();

    // Call due tasks
    tasks.forEach(function(task) {
      if (task.due <= currentTime)
        task.fn();
    });

    // Then remove them from the list.
    tasks = tasks.filter(function(task) { return task.due > currentTime; });

    // More tasks pending, keep calling the scheduler.
    if (tasks.length > 0) {
      window.requestAnimationFrame(scheduler);
    }
  }

  return {
    setTimeout: function(fn, delayMillis) {
      const id = nextTaskId;
      nextTaskId += 1;
      tasks.push({
        id: id,
        due: now() + delayMillis,
        fn: fn
      });
      if (tasks.length === 1) {
        window.requestAnimationFrame(scheduler);
      }
      return id;
    },
    clearTimeout: function(id) {
      tasks = tasks.filter(function(t) { return t.id !== id; });
    }
  }
}

override-set-timeout-with-internal-time.js

function customTimeout(audioContext) {

  let tasks = [];
  let nextTaskId = 1;

  let t0 = 0;
  let now = 0;
  function updateInternalTime() {
    const t1 = audioContext.currentTime * 1000; // somehow
    const deltaT = t1 - t0;
    if (deltaT < 0) { // the time counter was reset?
      return; // don't increase time.
    }
    if (deltaT > 1000) { // the app was backgrounded or frozen
      deltaT = 1000; // don't allow big jumps in time
    }
    now += deltaT;
  }

  function scheduler() {
    updateInternalTime();

    // Call due tasks
    tasks.forEach(function(task) {
      if (task.due <= now)
        task.fn();
    });

    // Then remove them from the list.
    tasks = tasks.filter(function(task) { return task.due > now; });

    // More tasks pending, keep calling the scheduler.
    if (tasks.length > 0) {
      t0 = audioContext.currentTime * 1000;
      window.requestAnimationFrame(scheduler);
    }
  }

  return {
    setTimeout: function(fn, delayMillis) {
      const id = nextTaskId;
      nextTaskId += 1;
      tasks.push({
        id: id,
        due: now + delayMillis,
        fn: fn
      });
      if (tasks.length === 1) {
        t0 = audioContext.currentTime * 1000;
        window.requestAnimationFrame(scheduler);
      }
      return id;
    },
    clearTimeout: function(id) {
      tasks = tasks.filter(function(t) { return t.id !== id; });
    }
  }
}