78 lines
2.2 KiB
Markdown
78 lines
2.2 KiB
Markdown
---
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id: 5cdafbc32913098997531680
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title: 通過 resolve 和 reject 完成 Promise
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challengeType: 1
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forumTopicId: 301196
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dashedName: complete-a-promise-with-resolve-and-reject
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---
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# --description--
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Promise 有三個狀態:`pending`、`fulfilled` 和 `rejected`。 上一個挑戰裏創建的 promise 一直阻塞在 `pending` 狀態裏,因爲沒有調用 promise 的完成方法。 Promise 提供的 `resolve` 和 `reject` 參數就是用來結束 promise 的。 Promise 成功時調用 `resolve`,promise 執行失敗時調用 `reject`, 如下文所述,這些方法需要有一個參數。
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```js
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const myPromise = new Promise((resolve, reject) => {
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if(condition here) {
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resolve("Promise was fulfilled");
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} else {
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reject("Promise was rejected");
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}
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});
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```
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上面的示例使用字符串作爲這些函數的參數,但參數實際上可以是任何格式。 通常,它可能是一個包含數據的對象,你可以將它放在網站或其他地方。
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# --instructions--
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使 promise 可以處理成功和失敗情況。 如果 `responseFromServer` 是 `true`,調用 `resolve` 方法使 promise 成功。 給 `resolve` 傳遞值爲 `We got the data` 的字符串。 如果 `responseFromServer` 是 `false`, 使用 `reject` 方法並傳入值爲 `Data not received` 的字符串。
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# --hints--
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當 `if` 條件是 `true` 時應該執行 `resolve`。
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```js
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assert(
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code.match(/if\s*\(\s*responseFromServer\s*\)\s*{\s*resolve\s*\(\s*('|"|`)We got the data\1\s*\)(\s*|\s*;\s*)}/g)
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);
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```
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當 `if` 條件是 `false` 時應該執行 `reject`。
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```js
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assert(
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code.match(/}\s*else\s*{\s*reject\s*\(\s*('|"|`)Data not received\1\s*\)(\s*|\s*;\s*)}/g)
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);
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```
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# --seed--
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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 represents a response from a server
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let responseFromServer;
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if(responseFromServer) {
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// Change this line
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} else {
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// Change this line
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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 represents a response from a server
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let responseFromServer;
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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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