101 lines
2.0 KiB
Markdown
101 lines
2.0 KiB
Markdown
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---
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id: 5cdafbe72913098997531682
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title: 使用 catch 處理 Promise 失敗的情況
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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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當 promise 失敗時會調用 `catch` 方法。 當 promise 的 `reject` 方法執行時會直接調用。 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` 是傳入 `reject` 方法的參數。
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# --instructions--
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給 promise 添加 `catch` 方法。 用 `error` 作爲回調函數的參數，並把 `error` 打印到控制檯。
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# --hints--
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應該在 promise 上調用 `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` 方法應該有一個回調函數，回調函數參數爲 `error`。
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```js
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assert(errorIsParameter);
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```
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應該打印 `error` 到控制檯。
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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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