Promise and callback example

promise-callback-sample.js

var promise = canReject => new Promise((resolve, reject) => canReject ? reject('bye') : resolve('hi'))
const thenCallback = message => console.log(message);
const catchCallback = message => console.log(message);
promise()
.then(thenCallback)
.catch(catchCallback)
promise(true)
.then(thenCallback)
.catch(catchCallback)

var greet = callback => typeof callback === 'function' && callback('hi')
var callback = prefix => prefix + ' Jai';
var greetJai = greet(callback);