How to expect a javascript function inside another one?

Question:

I have the hypothetical situation:

function fTeste2(valor) {
  setTimeout(function() {
    alert("Hello");
  }, 3000);
  return valor + 5;
}

function fTeste1(valor) {
  return fTeste2(valor);
}

alert(fTeste1(10));

Note that function 2 sends the sum without having finished the entire internal process, I know that if I put the sum inside the settimeout it will wait and give me the result, but function 2 exemplifies a function with several operations, this in another language would wait for the end of function 2, but in javascript this does not occur, how to solve it?

Answer:

A simple way to work around this problem is to work with callbacks . Basically, a function that will be executed when an operation completes. In your case, instead of waiting for the return of fTeste1 to call the alert function, you can pass it as a callback , as in the code below, indicating: when it fTeste2 the execution of fTeste2 , execute alert with the parameter passed.

function fTeste2(valor, callback) {
  setTimeout(function() {
    alert("Hello");
    callback(valor + 5);
  }, 3000);
}

function fTeste1(valor, callback) {
  fTeste2(valor, callback);
}

fTeste1(10, alert);

When running the code, you will see that the alert(15) is only executed after the alert("hello") , as desired.