95 lines
2.2 KiB
Markdown
95 lines
2.2 KiB
Markdown
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---
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id: 56bbb991ad1ed5201cd392cf
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title: 用函數編寫可重用代碼
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challengeType: 1
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videoUrl: 'https://scrimba.com/c/cL6dqfy'
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forumTopicId: 18378
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dashedName: write-reusable-javascript-with-functions
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---
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# --description--
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在 JavaScript 中，我們可以把代碼的重複部分抽取出來，放到一個函數 （<dfn>functions</dfn>）中。
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舉個例子：
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```js
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function functionName() {
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console.log("Hello World");
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}
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```
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你可以通過函數名加上後面的小括號來調用（<dfn>invoke</dfn>）這個函數，就像這樣： `functionName();` 每次調用函數時，它都會在控制檯上打印消息 `Hello World`。 每次調用函數時，大括號之間的所有代碼都將被執行。
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# --instructions--
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<ol><li>先創建一個名爲 <code>reusableFunction</code> 的函數，這個函數可以打印 <code>"Hi World"</code> 到控制檯上。</li><li>然後調用這個函數。</li></ol>
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# --hints--
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`reusableFunction` 應該是一個函數。
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```js
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assert(typeof reusableFunction === 'function');
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```
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如果調用 `reusableFunction`，應該在控制檯輸出字符串 `Hi World`。
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```js
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assert(testConsole());
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```
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在定義 `reusableFunction` 之後，就應該調用它。
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```js
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const functionStr = reusableFunction && __helpers.removeWhiteSpace(reusableFunction.toString());
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const codeWithoutFunction = __helpers.removeWhiteSpace(code).replace(/reusableFunction\(\)\{/g, '');
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assert(/reusableFunction\(\)/.test(codeWithoutFunction));
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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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function testConsole() {
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var logOutput = "";
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var originalConsole = console;
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var nativeLog = console.log;
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var hiWorldWasLogged = false;
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console.log = function (message) {
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if(message === 'Hi World') {
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console.warn(message)
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hiWorldWasLogged = true;
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}
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if(message && message.trim) logOutput = message.trim();
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if(nativeLog.apply) {
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nativeLog.apply(originalConsole, arguments);
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} else {
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var nativeMsg = Array.prototype.slice.apply(arguments).join(' ');
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nativeLog(nativeMsg);
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}
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};
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reusableFunction();
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console.log = nativeLog;
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return hiWorldWasLogged;
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}
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```
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## --seed-contents--
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```js
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```
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# --solutions--
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```js
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function reusableFunction() {
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console.log("Hi World");
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}
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reusableFunction();
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```
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