JSFiddle - React, Tailwind, and code Playground

JavaScript

function f1(arg1a, arg1b) {

  return $.Deferred(function(dfd) {
    //do something with arg1a, arg1b
    dfd.resolve(arg1a * 5, arg1b * 10)
  }).promise();
}

function f2(arg2a, arg2b) {
  // Do something with arg2a and arg2b AFTER f1 has fully run.
  console.log(arg2a, arg2b)
}

f1(1, 2)
.then(f2)
// handle errors
.catch(function(err) { // alternatively use `.fail()`
  console.log(err)
})