async-await内で並列処理

async-await内で並列的に実行したい場合

function sleepAndSay(time: number, msg: string): Promise<void> {
    return new Promise<void>(resolve => {
        setTimeout(() => {
            console.log(msg)
            resolve();
        }, time);
    });
}

async function main() {
    await sleepAndSay(200, 'test1')
    await sleepAndSay(100, 'test2')
    await Promise.all([
        (async () => {
            await sleepAndSay(50, 'in promise.all 1-1');
            await sleepAndSay(40, 'in promise.all 1-2');
            await sleepAndSay(40, 'in promise.all 1-3');
            return;
        })(),
        (async () => {
            await  sleepAndSay(30, 'in promise.all 2-1');
            await  sleepAndSay(20, 'in promise.all 2-2');
            await  sleepAndSay(20, 'in promise.all 2-3');
            return;
        })(),
    ])

    await sleepAndSay(100, 'test3')

}

実行結果

test1
test2
in promise.all 2-1
in promise.all 1-1
in promise.all 2-2
in promise.all 2-3
in promise.all 1-2
in promise.all 1-3
test3

目的通り動くけどPromise.allはpromiseを受け取る。
async はpromiseを 返す 関数を作るので all内で実行する必要があり、(が少しうざい。

改善案としてpararels関数を作る

function pararels(...promises: (() => Promise<any>)[]) {
  return Promise.all(promises.map(p => p()));
}

async function main2() {
    await sleepAndSay(200, 'test1')
    await sleepAndSay(100, 'test2')
    await pararels(
        async () => {
            await sleepAndSay(50, 'in promise.all 1-1');
            await sleepAndSay(40, 'in promise.all 1-2');
            await sleepAndSay(40, 'in promise.all 1-3');
            return;
        },
        async () => {
            await  sleepAndSay(30, 'in promise.all 2-1');
            await  sleepAndSay(20, 'in promise.all 2-2');
            await  sleepAndSay(20, 'in promise.all 2-3');
            return;
        },
    )

    await sleepAndSay(100, 'test3')

}

実行結果

test1
test2
in promise.all 2-1
in promise.all 1-1
in promise.all 2-2
in promise.all 2-3
in promise.all 1-2
in promise.all 1-3
test3

少し楽になった