An interesting article about timers in JS: https://jakearchibald.com/2015/tasks-microtasks-queues-and-schedules/

setImmediate(...) is Microsoft nonsense.

https://developer.mozilla.org/en-US/docs/Web/API/Window/setImmediate

Passing arguments:

// We can use: setTimeout(func, delay, arg1, arg2, arg3, ...)

I suggest avoid doing that. First, it is not clear if it works in most of the browsers: https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/setTimeout#Browser_compatibility

Secondly it is a specific way to pass parameters that works for setTimeout, and not for other functions (like array.forEach).

The general method is to use .bind(...)(almost obsolete now) or a (arrow) function:

// solution1.js with arrow funtions
const theOneFunc = delay => {
  console.log('Hello after ' + delay + ' seconds');
};
setTimeout(() => theOneFunc(4), 4 * 1000);
setTimeout(() => theOneFunc(8), 8 * 1000);

Finally, the this problem is more related to the way a function is called rather than to the caller.

const obj = { 
  id: '42',
  whoCalledMe() {
    console.log('Caller is', this);
  }
};
obj.whoCalledMe(); // Logs Caller is {id: "42", whoCalledMe: ƒ}
const method = obj.whoCalledMe;
method(); // Logs Caller is Window {...}

In the example

setTimeout(obj.whoCalledMe, 0);

you pass the function whoCalledMe to setTimeout , not the method of the object obj . That’s why you loose the this context, which originally was obj .