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author | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:43:23 -0500 |
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committer | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:43:23 -0500 |
commit | 218934fa2ed1c702a6d3923d2aa2cc6b43c48684 (patch) | |
tree | a9ef8ac1e1b8fe4207b6d64d3841bfb8990b6fd0 /files/zh-tw/web/javascript/reference/statements/export/index.html | |
parent | 074785cea106179cb3305637055ab0a009ca74f2 (diff) | |
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diff --git a/files/zh-tw/web/javascript/reference/statements/export/index.html b/files/zh-tw/web/javascript/reference/statements/export/index.html new file mode 100644 index 0000000000..195d4bed7f --- /dev/null +++ b/files/zh-tw/web/javascript/reference/statements/export/index.html @@ -0,0 +1,165 @@ +--- +title: export +slug: Web/JavaScript/Reference/Statements/export +translation_of: Web/JavaScript/Reference/Statements/export +--- +<div>{{jsSidebar("Statements")}}</div> + +<p><span class="seoSummary">用 <strong>export</strong> 可以指派函式、物件或變數,透過 {{jsxref("Statements/import", "import")}} 宣告給外部檔案引用。</span></p> + +<p>導出的模塊都會處於{{jsxref("Strict_mode","嚴謹模式")}},無論是否有所宣告。導出宣告無法使用嵌入式腳本(embedded script)。</p> + +<h2 id="語法">語法</h2> + +<pre class="syntaxbox">export { <var>name1</var>, <var>name2</var>, …, <var>nameN</var> }; +export { <var>variable1</var> as <var>name1</var>, <var>variable2</var> as <var>name2</var>, …, <var>nameN</var> }; +// 用 var, const 也通 +export let <var>name1</var>, <var>name2</var>, …, <var>nameN</var>; +export let <var>name1</var> = …, <var>name2</var> = …, …, <var>nameN</var>; + +// 底下的 function 用 class, function* 也可以 +export default <em>expression</em>; +export default function (…) { … } +export default function name1(…) { … } + +export { <var>name1</var> as default, … }; +export * from …; +export { <var>name1</var>, <var>name2</var>, …, <var>nameN</var> } from …; +export { <var>import1</var> as <var>name1</var>, <var>import2</var> as <var>name2</var>, …, <var>nameN</var> } from …;</pre> + +<dl> + <dt><code>nameN</code></dt> + <dd>外部檔案使用 <code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/import">import</a></code> 時,用於辨認的名稱。</dd> +</dl> + +<h2 id="使用說明">使用說明</h2> + +<p>有兩種使用 export 的方式,<strong>named</strong> 與 <strong>default</strong>。每個模組中可以有多個 named exports, 但只能有一個 default export。每種 export 都對應到一個先前說的語法。</p> + +<ul> + <li>Named exports: + <pre class="brush: js">// 前面已經宣告的函式可以這樣輸出 +export { myFunction }; + +// 輸出常數 +export const foo = Math.sqrt(2); </pre> + </li> + <li>預設 export (一個 js 檔案只能有一個): + <pre class="brush: js">export default function() {} +// 或是 '<em>export default class {}</em>' +// 結尾不用分號</pre> + </li> +</ul> + +<p>Named exports 在輸出多個值的時候很有用,在 import 的時候, 會強制根據使用相同的物件名稱.</p> + +<p>但如果是 default export 則可以用任意的名字輸出.</p> + +<pre class="syntaxbox">export default k = 12; // 在test.js中這樣子寫 + +import m from './test' // 注意這邊因為 export default 的關係, 可以用任意名字 import 原先的k出來 + +console.log(m); // will log 12 +</pre> + +<p>以下語法並不會導出所有被引入的模塊:</p> + +<pre>export * from …;</pre> + +<p>你必須額外引入它的預設輸出,再導出之:</p> + +<pre>import mod from "mod"; +export default mod;</pre> + +<h2 id="使用範例">使用範例</h2> + +<h3 id="輸出命名過的變數">輸出命名過的變數</h3> + +<p>模塊內可以這樣用:</p> + +<pre class="brush: js">// module "my-module.js" +function cube(x) { + return x * x * x; +} +const foo = Math.PI + Math.SQRT2; +var graph = { + options:{ + color:'white', + thickness:'2px' + }, + draw: function(){ + console.log('From graph draw function'); + } +} +export { cube, foo, graph }; +</pre> + +<p>在另一個腳本就會變成這樣:</p> + +<pre class="brush: js">//You should use this script in html with the type module , +//eg ''<script type="module" src="demo.js"></script>", +//open the page in a httpserver,otherwise there will be a CORS policy error. +//script demo.js + +import { cube, foo, graph } from 'my-module'; +graph.options = { + color:'blue', + thickness:'3px' +}; +graph.draw(); +console.log(cube(3)); // 27 +console.log(foo); // 4.555806215962888</pre> + +<h3 id="使用預設輸出">使用預設輸出</h3> + +<p>如果我們要輸出單獨的函式、物件、class 或當做 fallback 值來輸出的話,就可以用預設輸出:</p> + +<pre class="brush: js">// module "my-module.js" +export default function cube(x) { + return x * x * x; +} +</pre> + +<p>外部檔案的 import 用法:</p> + +<pre class="brush: js">import cube from 'my-module'; +console.log(cube(3)); // 27 +</pre> + +<p>Note 注意預設輸出不能使用 var, let , const。</p> + +<h2 id="規範">規範</h2> + +<table class="standard-table"> + <tbody> + <tr> + <th scope="col">規範</th> + <th scope="col">狀態</th> + <th scope="col">註解</th> + </tr> + <tr> + <td>{{SpecName('ES2015', '#sec-exports', 'Exports')}}</td> + <td>{{Spec2('ES2015')}}</td> + <td>初始定義。</td> + </tr> + <tr> + <td>{{SpecName('ESDraft', '#sec-exports', 'Exports')}}</td> + <td>{{Spec2('ESDraft')}}</td> + <td></td> + </tr> + </tbody> +</table> + +<h2 id="瀏覽器相容性">瀏覽器相容性</h2> + + + +<p>{{Compat("javascript.statements.export")}}</p> + +<h2 id="參見">參見</h2> + +<ul> + <li>{{jsxref("Statements/import", "import")}}</li> + <li><a href="https://hacks.mozilla.org/2015/08/es6-in-depth-modules/">ES6 in Depth: Modules</a>, Hacks blog post by Jason Orendorff</li> + <li><a href="http://exploringjs.com/es6/ch_modules.html">Axel Rauschmayer's book: "Exploring JS: Modules"</a></li> +</ul> |