typescript 返回 Promise<void> 的异步函数在块的末尾是否有隐式返回？
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Does a async function which returns Promise<void> have an implicit return at the end of a block?
提问by Gala
public async demo(): Promise<void> {
// Do some stuff here
// Doing more stuff
// ...
// End of block without return;
}
Is a new Promise<void>returned implicitely at the end of the block in TypeScript/ES6?
Promise<void>在 TypeScript/ES6 的块末尾是否隐式返回了一个 new ？
Example for boolean type:
布尔类型示例：
class Test {
public async test(): Promise<boolean> {
return true;
}
public main(): void {
this.test().then((data: boolean) => {
console.log(data);
});
}
}
new Test().main();
This prints trueto the console because a returninside of a async function creates a new Promiseand calls resolve()on it with the returned data. What happens with a Promise<void>?
这会打印true到控制台，因为return异步函数的内部创建了一个新函数Promise并resolve()使用返回的数据调用它。会发生什么Promise<void>？
回答by basarat
What happens with a Promise
Promise 会发生什么
Same thing with a function that returns void. A voidfunction returns undefined. A Promise<void>resolves to an undefined.
与返回void. 一个void函数返回undefined。APromise<void>解析为undefined。
function foo(){}; console.log(foo()); // undefined
async function bar(){}; bar().then(res => console.log(res)); // undefined
