回答編集履歴
2
stateClone
answer
CHANGED
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@@ -137,4 +137,26 @@
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- [deep-copy-object.js: オブジェクトをディープコピー](https://gist.github.com/think49/96e8fc064b917287cadb1dfacc39695c)
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139
139
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140
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完全な deep copy ではなく、変数 `state` 特化のコードで良ければ、次のように書けます。
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141
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142
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```JavaScript
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143
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const state = {
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'001': [
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{id: '001', score: 142},
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{id: '001', score: 112}
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147
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],
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'010': [
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{id: '010', score: 142},
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{id: '010', score: 112}
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]
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};
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154
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const stateClone = Object.entries(state).reduce((state, entry) => {
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state[entry[0]] = entry[1].map(Object.assign.bind(null, {}));
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return state;
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}, state);
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158
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console.log(JSON.stringify(state) === JSON.stringify(stateClone)); // true
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```
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Re: hayatomo さん
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1
参照透過性
answer
CHANGED
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@@ -1,3 +1,5 @@
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1
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### コード
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2
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1
3
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シャローコピーで十分なような。
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2
4
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5
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```JavaScript
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@@ -55,6 +57,74 @@
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console.log(JSON.stringify(state)); // {"100":[{"id":"100","score":132},{"id":"100","score":482}],"001":[{"id":"001","score":142},{"id":"001","score":112},{"id":"001","score":100},{"id":"001","score":40}],"010":[{"id":"010","score":142},{"id":"010","score":112}]}
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```
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60
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> 副作用がないというか、参照透過性？のある純粋関数を作りたいのです。
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61
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62
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63
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```JavaScript
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64
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'use strict';
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65
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const payload = [
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66
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{id: '001', score: 100},
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{id: '001', score: 40},
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{id: '100', score: 132},
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{id: '100', score: 482}
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70
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];
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const state = {
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'001': [
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{id: '001', score: 142},
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{id: '001', score: 112}
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],
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'010': [
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{id: '010', score: 142},
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{id: '010', score: 112}
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]
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};
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var expectedResults = {
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84
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'100': [
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85
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{ id: '100', score: 132 },
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86
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{ id: '100', score: 482 }
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87
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],
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88
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89
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'001': [
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90
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{ id: '001', score: 142 },
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{ id: '001', score: 112 },
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{ id: '001', score: 100 },
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{ id: '001', score: 40 }
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],
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'010': [
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{ id: '010', score: 142 },
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{ id: '010', score: 112 }
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]
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100
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};
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function sample (payload, state) {
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const hasOwnProperty = Object.prototype.hasOwnProperty;
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const results = JSON.parse(JSON.stringify(state));
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for (let data of payload) {
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const id = data.id;
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data = Object.assign({}, data);
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if (!hasOwnProperty.call(state, id)) {
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results[id] = [data];
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} else {
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results[id].push(data);
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}
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}
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return results;
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}
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const results = sample(payload, state);
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console.log(JSON.stringify(state) === JSON.stringify(expectedResults)); // true
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console.log(JSON.stringify(state)); // {"100":[{"id":"100","score":132},{"id":"100","score":482}],"001":[{"id":"001","score":142},{"id":"001","score":112},{"id":"001","score":100},{"id":"001","score":40}],"010":[{"id":"010","score":142},{"id":"010","score":112}]}
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```
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125
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126
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### Deep Copy
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127
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58
128
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> //(1)Deep Copyするには？（ライブラリで解決する方法は既に把握済みですが、ライブラリを使わない場合はどう書くのか？
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プリミティブ値の集合なら、
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