First Example of a Javascript Promise (Tutorial)

promiseExplanation.js

//First code about promises
let promiseToCleanTheRoom = new Promise(function(resolve, reject){
	//Resolve: Means I am fullfilling this promise (resolving it).
	//Reject: Promise is not Fullfilled in given time or constraint.

	//HERE IS CLEANING THE ROOM CODE.... 
	//After doing this, clean's value gets set.

	let isClean = true; //Here you control resolve and reject in this example.

	if(isClean){
		resolve('Clean');
	} else {
		reject('Not Clean');
	}
});

//This fires when promise is resolved
promiseToCleanTheRoom.then(function(fromResolve){
//fromResolve receives argument inside the resolve function (in this case 'Clean')
	console.log('The room is ' + fromResolve);
}).catch(function(fromReject){
//same applies to fromReject
	console.log('The room is ' + fromReject);
});

To see results: Check in JSFiddle and open the dev tools console.