JavaScript Async Await Sequential and Parallel Test

async-await-test.js

async function testSequential() {
    async function f1 (){
        let promise = new Promise((resolve, reject) => {
            setTimeout(()=>{resolve(2)}, 2000);
        });
        return promise;
    }
    async function f2 (){
        let promise = new Promise((resolve, reject) => {
            setTimeout(()=>{resolve(2)}, 2000);
        });
        return promise;
    }
    console.time("first await finished");
    let r1 = await f1();
    console.timeEnd("first await finished");
    console.time("second await finished");
    let r2 = await f2();
    console.timeEnd("second await finished");
    return r1 + r2;
}
async function testParallel() {
    async function f1 (){
        let promise = new Promise((resolve, reject) => {
            setTimeout(()=>{resolve(2)}, 2000);
    });
        return promise;
    }
    async function f2 (){
        let promise = new Promise((resolve, reject) => {
            setTimeout(()=>{resolve(2)}, 2000);
    });
        return promise;
    }
    console.time("await finished");
    let r1 = await Promise.all([f1(),f2()]);
    console.timeEnd("await finished");
    return r1[0] + r1[1];
}
async function start(){
    console.time("testParallel");
    let result = await testParallel();
    console.log(result);
    console.timeEnd("testParallel");
    console.time("testSequential");
    result = await testSequential();
    console.log(result);
    console.timeEnd("testSequential");
}
start();