const foo = (callback) => {
  setTimeout(() => {
    callback("A");
  }, Math.floor(Math.random() * 100));
};
 
const bar = (callback) => {
  setTimeout(() => {
    callback("B");
  }, Math.floor(Math.random() * 100));
};
 
const baz = (callback) => {
  setTimeout(() => {
    callback("C");
  }, Math.floor(Math.random() * 100));
};
 
const result = () => {};
 
result(); // ['C', 'A', 'B']