freeCodeCamp/curriculum/challenges/chinese/02-javascript-algorithms-and-data-structures/es6/handle-a-fulfilled-promise-with-then.md

id, challengeType, forumTopicId, title

id	challengeType	forumTopicId	title
5cdafbd72913098997531681	1	301203	在 then 中处理 Promise 完成的情况

Description

当程序需要花费未知的时间才能完成时 Promise 很有用（比如，一些异步操作），一般是网络请求。网络请求会花费一些时间，当结束时需要根据服务器的响应执行一些操作。这可以用 then 方法来实现，当 promise 完成 resolve 时会触发 then 方法。例子如下：

myPromise.then(result => {
  // do something with the result.
});

result 即传入 resolve 方法的参数。

Instructions

给 promise 添加 then 方法。用 result 做为回调函数的参数并将 result 打印在控制台。

Tests

tests:
  - text: 应该给 promise 方法调用 <code>then</code> 方法。
    testString: assert(codeWithoutSpaces.match(/(makeServerRequest|\))\.then\(/g));
  - text: <code>then</code> 方法应该有一个回调函数，回调函数参数为 <code>result</code>。
    testString: assert(resultIsParameter);
  - text: 应该打印 <code>result</code> 到控制台。
    testString: assert(resultIsParameter && codeWithoutSpaces.match(/\.then\(.*?result.*?console.log\(result\).*?\)/));

Challenge Seed

const makeServerRequest = new Promise((resolve, reject) => {
  // responseFromServer is set to true to represent a successful response from a server
  let responseFromServer = true;
	
  if(responseFromServer) {
    resolve("We got the data");
  } else {	
    reject("Data not received");
  }
});

After Test

const codeWithoutSpaces = code.replace(/\s/g, '');
const resultIsParameter = /\.then\((function\(result\){|result|\(result\)=>)/.test(codeWithoutSpaces);

Solution

const makeServerRequest = new Promise((resolve, reject) => {
  // responseFromServer is set to true to represent a successful response from a server
  let responseFromServer = true;
	
  if(responseFromServer) {
    resolve("We got the data");
  } else {	
    reject("Data not received");
  }
});

makeServerRequest.then(result => {
  console.log(result);
});