93 lines
2.1 KiB
Markdown
93 lines
2.1 KiB
Markdown
---
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id: 5cdafbd72913098997531681
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title: 用 then 处理 Promise 完成的情况
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challengeType: 1
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forumTopicId: 301203
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dashedName: handle-a-fulfilled-promise-with-then
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---
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# --description--
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当程序需要花费未知的时间才能完成时（比如一些异步操作），一般是服务器请求，promise 很有用。 服务器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：
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```js
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myPromise.then(result => {
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});
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```
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`result` 即传入 `resolve` 方法的参数。
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# --instructions--
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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。
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# --hints--
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应该给 promise 方法调用 `then` 方法。
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```js
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assert(
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__helpers.removeWhiteSpace(code).match(/(makeServerRequest|\))\.then\(/g)
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);
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```
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`then` 方法应该有一个回调函数，回调函数参数为 `result`。
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```js
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assert(resultIsParameter);
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```
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应该打印 `result` 到控制台。
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```js
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assert(
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resultIsParameter &&
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__helpers
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.removeWhiteSpace(code)
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.match(/\.then\(.*?result.*?console.log\(result\).*?\)/)
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);
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```
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# --seed--
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## --after-user-code--
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```js
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const resultIsParameter = /\.then\((function\(result\){|result|\(result\)=>)/.test(__helpers.removeWhiteSpace(code));
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```
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## --seed-contents--
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```js
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const makeServerRequest = new Promise((resolve, reject) => {
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// responseFromServer is set to true to represent a successful response from a server
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let responseFromServer = true;
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if(responseFromServer) {
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resolve("We got the data");
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} else {
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reject("Data not received");
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}
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});
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```
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# --solutions--
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```js
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const makeServerRequest = new Promise((resolve, reject) => {
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// responseFromServer is set to true to represent a successful response from a server
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let responseFromServer = true;
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if(responseFromServer) {
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resolve("We got the data");
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} else {
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reject("Data not received");
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}
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});
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makeServerRequest.then(result => {
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console.log(result);
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});
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```
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