working with async await

index.js

/**
 * implementing return value of setTimeout() from callback to promise
 * @param ms
 * @returns {Promise<function>}
 */
const sleep = function (ms) {
    // 4.) task 1: we create a new promise and call setTimeout(), 
    //     set timeout creates a new taks 2 that will run after taks 1 has finished & 1500 milliseconds have passed
    // new Promise(function(resolve, reject) { ... });
    return new Promise(resolve => {
        // 6.) task 2: as task 1 has stopped, the event loop goes on with task 2 after 1500 milliseconds have passed,
        //     we console.log('2');
        setTimeout(() => {console.log('2'); resolve();}, ms);
    });
};

async function allowAwait(){
    // 2.) taks 1: async functions always return a promise, meaning that we can use await inside 
    //      the function to 'wait' for some async taks
    console.log('1');
    // 3.) task 1: we console.log('1'); and now call sleep(1500)
    // 5.) task 1: we come back from the sleep(1500) function call and hit await
    //             and will now stop task 1 (we are not blocking, we just give back to the event loop) to await task 2
    await sleep(1500);
    // 7.) task 1: after task has finished, task 1 continues and executes console.log('3');
    console.log('3');
}

// 1.) task 1: we start here
allowAwait();

/* => Output:
 * 1
 * 2
 * 3
 * Working with promises does not only allow us to chain work with then() but also to await the promise directly.
 */