arol

const randomNumber = () => {
  return Math.random();
}

// 1. Make it wait for 1 sec. with `setTimeout`
const timeoutRandomNumber = (cb) => {
  setTimeout(() => {
    cb(null, randomNumber())
  }, 1000);
}

arol

Babel + Typescript in the

1. Install babel (https://babeljs.io/setup#installation)
2. Add typescript (https://blogs.msdn.microsoft.com/typescript/2018/08/27/typescript-and-babel-7/)
3. Change all files from .js extension to .ts.
4. Set up the development process to be babel-node --extensions '.ts,.tsx’ index.ts
5. Install tslint. (https://palantir.github.io/tslint/usage/cli/). Here you have a tslint.json file example:

{
 "extends": "tslint:recommended",