--- id: 5cdafbe72913098997531682 title: 使用 catch 處理 Promise 失敗的情況 challengeType: 1 forumTopicId: 301204 dashedName: handle-a-rejected-promise-with-catch --- # --description-- 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: ```js myPromise.catch(error => { }); ``` `error` 是傳入 `reject` 方法的參數。 # --instructions-- 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。 # --hints-- 應該在 promise 上調用 `catch` 方法。 ```js assert( __helpers.removeWhiteSpace(code).match(/(makeServerRequest|\))\.catch\(/g) ); ``` `catch` 方法應該有一個回調函數,回調函數參數爲 `error`。 ```js assert(errorIsParameter); ``` 應該打印 `error` 到控制檯。 ```js assert( errorIsParameter && __helpers .removeWhiteSpace(code) .match(/\.catch\(.*?error.*?console.log\(error\).*?\)/) ); ``` # --seed-- ## --after-user-code-- ```js const errorIsParameter = /\.catch\((function\(error\){|error|\(error\)=>)/.test(__helpers.removeWhiteSpace(code)); ``` ## --seed-contents-- ```js const makeServerRequest = new Promise((resolve, reject) => { // responseFromServer is set to false to represent an unsuccessful response from a server let responseFromServer = false; if(responseFromServer) { resolve("We got the data"); } else { reject("Data not received"); } }); makeServerRequest.then(result => { console.log(result); }); ``` # --solutions-- ```js const makeServerRequest = new Promise((resolve, reject) => { // responseFromServer is set to false to represent an unsuccessful response from a server let responseFromServer = false; if(responseFromServer) { resolve("We got the data"); } else { reject("Data not received"); } }); makeServerRequest.then(result => { console.log(result); }); makeServerRequest.catch(error => { console.log(error); }); ```