101 lines
2.0 KiB
Markdown
101 lines
2.0 KiB
Markdown
---
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id: 5cdafbe72913098997531682
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title: 使用 catch 处理 Promise 失败的情况
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challengeType: 1
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forumTopicId: 301204
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dashedName: handle-a-rejected-promise-with-catch
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---
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# --description--
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当 promise 失败时会调用 `catch` 方法。 当 promise 的 `reject` 方法执行时会直接调用。 用法如下:
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```js
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myPromise.catch(error => {
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});
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```
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`error` 是传入 `reject` 方法的参数。
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# --instructions--
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给 promise 添加 `catch` 方法。 用 `error` 作为回调函数的参数,并把 `error` 打印到控制台。
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# --hints--
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应该在 promise 上调用 `catch` 方法。
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```js
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assert(
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__helpers.removeWhiteSpace(code).match(/(makeServerRequest|\))\.catch\(/g)
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);
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```
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`catch` 方法应该有一个回调函数,回调函数参数为 `error`。
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```js
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assert(errorIsParameter);
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```
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应该打印 `error` 到控制台。
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```js
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assert(
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errorIsParameter &&
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__helpers
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.removeWhiteSpace(code)
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.match(/\.catch\(.*?error.*?console.log\(error\).*?\)/)
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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 errorIsParameter = /\.catch\((function\(error\){|error|\(error\)=>)/.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 false to represent an unsuccessful response from a server
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let responseFromServer = false;
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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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# --solutions--
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```js
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const makeServerRequest = new Promise((resolve, reject) => {
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// responseFromServer is set to false to represent an unsuccessful response from a server
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let responseFromServer = false;
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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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makeServerRequest.catch(error => {
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console.log(error);
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});
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```
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