From 310fd066e91f454b990372ffa30e803cc8120975 Mon Sep 17 00:00:00 2001 From: Florian Merz Date: Thu, 11 Feb 2021 12:56:40 +0100 Subject: unslug zh-cn: move --- .../reference/statements/default/index.html | 120 --------------------- 1 file changed, 120 deletions(-) delete mode 100644 files/zh-cn/web/javascript/reference/statements/default/index.html (limited to 'files/zh-cn/web/javascript/reference/statements') diff --git a/files/zh-cn/web/javascript/reference/statements/default/index.html b/files/zh-cn/web/javascript/reference/statements/default/index.html deleted file mode 100644 index 12e076166c..0000000000 --- a/files/zh-cn/web/javascript/reference/statements/default/index.html +++ /dev/null @@ -1,120 +0,0 @@ ---- -title: default -slug: Web/JavaScript/Reference/Statements/default -tags: - - JavaScript - - Keyword -translation_of: Web/JavaScript/Reference/Statements/switch -translation_of_original: Web/JavaScript/Reference/Statements/default ---- -
{{jsSidebar("Statements")}}
- -
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default 关键字可以在 JavaScript 的两种情况下使用:在 {{jsxref("Statements/switch", "switch")}} ,或 {{jsxref("Statements/export", "export")}} 中。

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语法

- -

在{{jsxref("Statements/switch", "switch")}} 语句中使用:

- -
switch (expression) {
-  case value1:
-    //当表达式的值和value1匹配执行这里的语句
-    [break;]
-  default:
-    //当表达式的值没有匹配,执行这里的语句
-    [break;]
-}
- -

在{{jsxref("Statements/export", "export")}} 中使用:

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export default nameN 
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描述

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更多细节,参见

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示例

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switch语句中使用default

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在以下示例中,如果expr为“Oranges”或“Apples”,程序将匹配“Oranges”或“Apples”的值并执行相应的声明。在任何其它情况下,default关键字将执行关联的语句。

- -
switch (expr) {
-  case "Oranges":
-    console.log("Oranges are $0.59 a pound.");
-    break;
-  case "Apples":
-    console.log("Apples are $0.32 a pound.");
-    break;
-  default:
-    console.log("Sorry, we are out of " + expr + ".");
-}
- -

export语句中使用default

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如果要导出单个值或需要模块的回调值,则可以使用默认导出: 

- -
// module "my-module.js"
-let cube = function cube(x) {
-  return x * x * x;
-}
-export default cube;
-
- -

然后,在另一个脚本中,默认导出将直接被导入:

- -
// module "my-module.js"
-import myFunction from 'my-module';
-console.log(myFunction(3)); // 27
-
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规范

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SpecificationStatusComment
{{SpecName('ES6', '#sec-switch-statement', 'switch statement')}}{{Spec2('ES6')}}
{{SpecName('ES6', '#sec-exports', 'Exports')}}{{Spec2('ES6')}}
{{SpecName('ESDraft', '#sec-switch-statement', 'switch statement')}}{{Spec2('ESDraft')}}
{{SpecName('ESDraft', '#sec-exports', 'Exports')}}{{Spec2('ESDraft')}}
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浏览器兼容

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{{Compat("javascript.statements.default")}}

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See also

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