async/awaitとPromiseを試す

sample1.ts

// async/awaitとPromiseのサンプル

// Promiseを返す関数
const actionAsync = (result: number) => {
	const promise = new Promise<number>((resolve, reject) => {
		// 1秒後にresolveする
		setTimeout(() => resolve(result), 1000);
	});

	return promise;
};

// テスト用の関数
const testAcync = async () => {
	console.log("await1");
	const result1 = await actionAsync(1);
	console.log(`result1: ${result1}`);

	console.log("await2");
	const result2 = await actionAsync(2);
	console.log(`result2: ${result2}`);
};
testAcync();
/*
await1
result1: 1
await2
result2: 2
*/

sample2.ts

// async/awaitとPromise
// rejectした場合

// Promiseを返す関数
const actionAsync = (result: number) => {
	const promise = new Promise<number>((resolve, reject) => {
		// 1秒後にresolveまたはrejectする
		setTimeout(() => result < 0 ? reject("エラー") : resolve(result), 1000);
	});

	return promise;
};

// テスト用の関数
const testAcync = async () => {
	try {
		console.log("await1");
		const result1 = await actionAsync(1);
		console.log(`result1: ${result1}`);

		console.log("await2");
		const result2 = await actionAsync(-1);
		console.log(`result2: ${result2}`);
	} catch (error) {
		console.log(`error: ${error}`);
	}
};
testAcync();
/*
await1
result1: 1
await2
error: エラー
*/

sample3.ts

// async関数はPromiseを返す
// https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Statements/async_function

// 値を返すとresolveしたPromiseを返す
const resolveAsync = async (result: number) => result;

// 例外や値をスローした場合はrejectされたPromiseを返す
const rejectAsync = async (message: string) => {
	throw message;
}

// テスト用の関数
const testAcync = async () => {
	try {
		console.log("await1");
		const result1 = await resolveAsync(1);
		console.log(`result1: ${result1}`);

		console.log("await2");
		const result2 = await rejectAsync("エラー");
		console.log(`result2: ${result2}`);
	} catch (error) {
		console.log(`error: ${error}`);
	}
};
testAcync();
/*
await1
result1: 1
await2
error: エラー
*/

• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await