callback-to-promise.js

function getData(callback) {
  setTimeout(() => callback("hi"), 10);
}

function render(promiseData) {
  promiseData.then(data => console.log("data"));
}

// wrapper around getData() to make it return a promise
function getDataPromise() {
  return new Promise((resolve, reject) => {
    getData(resolve);
  });
}

// use render with the wrapper
render(getDataPromise());