定義済みの key の set() した時にエラーを発生させる new Map 互換オブジェクトを生成します。
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September 13, 2021 13:20
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const-map.js: 定義済みの `key` の `set()` した時にエラーを発生させる `new Map` 互換オブジェクトを生成します
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| /** | |
| * const-map-0.1.1.js | |
| * | |
| * | |
| * @version 0.1.1 | |
| * @author think49 | |
| * @url https://gist.github.com/think49/6776d8cebf8d4ca75c7b935aec4f4b82 | |
| * @license http://www.opensource.org/licenses/mit-license.php (The MIT License) | |
| */ | |
| 'use strict'; | |
| const ConstMap = (()=>{ | |
| const privateMap = new WeakMap; | |
| return class ConstMap { | |
| constructor (...params) { | |
| privateMap.set(this, new Map(...params)); | |
| } | |
| get (key) { | |
| return privateMap.get(this).get(key); | |
| } | |
| set (key, value) { | |
| const map = privateMap.get(this); | |
| const defError = new Error; | |
| defError.name = 'DefinitionError'; | |
| defError.message = 'Identifier \'' + key + '\' has already been declared'; | |
| if (map.has(key)) throw defError; | |
| return map.set(key, value); | |
| } | |
| has (key) { | |
| return privateMap.get(this).has(key); | |
| } | |
| keys () { | |
| return Array.from(privateMap.get(this).keys()); | |
| } | |
| values () { | |
| return Array.from(privateMap.get(this).values()); | |
| } | |
| entries () { | |
| return Array.from(privateMap.get(this).entries()); | |
| } | |
| }; | |
| })(); |
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| <!DOCTYPE html> | |
| <title>test</title> | |
| <style> | |
| </style> | |
| <script src="./const-map-0.1.1.js"></script> | |
| <script> | |
| 'use strict'; | |
| const cmap = new ConstMap([['foo',1],['bar',2],['baz',3]]); | |
| /** | |
| * Assertion | |
| */ | |
| console.assert(cmap.get('foo') === 1); | |
| console.assert(cmap.get('bar') === 2); | |
| console.assert(cmap.get('baz') === 3); | |
| console.assert(cmap.get('qux') === undefined); | |
| console.assert(cmap.has('foo') === true); | |
| console.assert(cmap.has('bar') === true); | |
| console.assert(cmap.has('baz') === true); | |
| console.assert(cmap.has('qux') === false); | |
| console.assert(JSON.stringify(cmap.keys()) === '["foo","bar","baz"]'); | |
| console.assert(JSON.stringify(cmap.values()) === '[1,2,3]'); | |
| console.assert(JSON.stringify(cmap.entries()) === '[["foo",1],["bar",2],["baz",3]]'); | |
| </script> | |
| <script> | |
| /** | |
| * DefinitionError | |
| */ | |
| cmap.set('foo', false); // DefinitionError: Identifier 'foo' has already been declared | |
| </script> |
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