How can I return the result of a callback function in a function?

Question

JavaScript

What needs to be done so that the do function returns the result of the getUrl function?

function do () {
    getUrl(function () {
        let a = 5;
        return a;
    }
}

console.log(do()); //5

Answer 1

Learn Promises

function do() {
  return new Promise((res, rej) => {
      getUrl(() => {
          const a = 5;
          res(a);
      })
  })
}

do().then(res => console.log(res));

Answer 2

Neither callback functions, nor promises, nor "promised functions", nor async functions can return values. Sic!