(async()=> {})();这是什么? [英] (async () => { })(); what is this?

问题描述

async function test() {
  (async () => {            
    var a = await this.test1();
    var b = await this.test2(a);
    var c = await this.test3(b);  
    this.doThis(a,b,c);                              
  })();
}

将方法(test1，test2，test3)放入async () => {})()是什么意思? 我发现它比

What does it mean to put methods (test1,test2,test3) inside async () => {})()? I find it faster than

async function test() {          
  var a = await this.test1();
  var b = await this.test2(a);
  var c = await this.test3(b);  
  this.doThis(a,b,c); 
}

使用它有什么缺点吗?

推荐答案

都返回一个诺言，但它们返回不同的诺言.

Both return a promise but they return different promises.

第一个将返回一个承诺，该承诺可能会在this.test1()的结果解析之前解决.

The first will return a promise that may resolve before this.test1()'s result resolves.

第二个返回的诺言只有在最终调用this.doThis(a,b,c);之后才能解决.

The second returns a promise that only resolves after the final call to this.doThis(a,b,c);.

这被称为" fire and忘记模式":

通常在应用程序开发中，您希望一个进程调用另一个线程并继续该进程流，而不用等待被调用线程的响应.这种模式称为即发即弃"模式.

Often in application development you want a process to call another thread and continue the process flow, without waiting for a response from the called thread. This pattern is called the "fire and forget" pattern.

您可以在

function logEventually(str) {
  return new Promise((resolve) => {
    setTimeout(() => {
      console.log(str);
      resolve(null);
    }, 0);
  });
}

async function a() {
  await logEventually('in a 1');
  await logEventually('in a 2');
  await logEventually('in a 3');
  return await logEventually('end of a');
}

async function b() {
  (async () => {
    await logEventually('in b 1');
    await logEventually('in b 2');
    await logEventually('in b 3');
  })();
  return await logEventually('end of b');
}

a();
b();

这篇关于(async()=> {})();这是什么?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！