101 lines
2.0 KiB
Markdown
101 lines
2.0 KiB
Markdown
---
|
|
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);
|
|
});
|
|
```
|