[Javascript / sync vs async promises] Synchronous vs Asynchronous Promises in Javascript #javascript

synchronous vs asynchronous promises.js

//asynchronous
; (async () => {

    console.time('testAsynchronous')
    let start = new Date()
    let hrstart = process.hrtime()

    let testAsync = await Promise.all([
        Promise.resolve(1),
        new Promise(async (resolve, reject) => {
            console.log("starting 2")
            return setTimeout(resolve, 1000, 2);
        }),
        new Promise(async (resolve, reject) => {
            console.log("starting 3")
            return setTimeout(resolve, 3000, 3);
        }),
        new Promise(async (resolve, reject) => {
            console.log("starting 4")
            return setTimeout(resolve, 4000, 4);
        }),
    ]);
    console.log(testAsync);
    let end = new Date() - start,
        hrend = process.hrtime(hrstart)

    console.info('Execution time: %dms', end)
    console.info('Execution time (hr): %ds %dms', hrend[0], hrend[1] / 1000000)
    console.timeEnd('testAsynchronous')

})();

//synchronous
(async () => {

    console.time('testSynchronous')
    let start = new Date()
    let hrstart = process.hrtime()

    let testSync = await Promise.all([
        Promise.resolve(1),
        await new Promise(async (resolve, reject) => {
            console.log("starting 2")
            return setTimeout(resolve, 1000, 2);
        }),
        await new Promise(async (resolve, reject) => {
            console.log("starting 3")
            return setTimeout(resolve, 3000, 3);
        }),
        await new Promise(async (resolve, reject) => {
            console.log("starting 4")
            return setTimeout(resolve, 4000, 4);
        }),
    ]);
    console.log(testSync);
    let end = new Date() - start,
        hrend = process.hrtime(hrstart)

    console.info('Execution time: %dms', end)
    console.info('Execution time (hr): %ds %dms', hrend[0], hrend[1] / 1000000)
    console.timeEnd('testSynchronous')
})();