Async function で非同期関数をリターンする場合に await の指定は必要？ `async functionA` functionA `await` functionADB // functionA async mainFunc() { const data = await functionA(); } async functionA () { return dummyAsyncFunc(); } // async functionA () { returnawait dummyAsyncFunc(); }

`await`main1main2

`await``async function`
`await``async function`PromisePromise
`Promise``await``string`
`Promise`
`Promise`~`then()`~`catch()`
`await`

`await`
I/O,
`await`
`then()`

`dummyAsyncFunction`1!


// : $ call api! →
async function main1() {
const res = await functionA1();
console.log(res);
console.log("")
}

// : $ → call api by awaiting!
async function main2() {
functionA2().then(res => console.log(res));
console.log("")
}

async function functionA1() {
return dummyAsyncFunction("call api");
}

async function functionA2() {
return await dummyAsyncFunction("call api by awaiting")
}

async function dummyAsyncFunction(message) {
return new Promise(resolve => {
setTimeout(() => {
resolve(message + "!")
}, (1000));
});
}