回答編集履歴
2
`Array#forEach`, `Array#reduce`, `Array#find` を使ったコードを追記
answer
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@@ -7,7 +7,7 @@
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/**
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* Array.prototype.indexOf 版
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*/
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-
function
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function sample_indexOf (array) {
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var keys = [],
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values = [],
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results = [];
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@@ -34,7 +34,7 @@
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/**
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* ObjectLiteral 版
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*/
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function
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function sample_ObjectLiteral (array) {
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var map = {},
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results = [];
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@@ -60,7 +60,7 @@
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* Map 版 (ES6)
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* @url https://github.com/paulmillr/es6-shim
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*/
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-
function
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function sample_map (array) {
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var map = new Map,
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results = [];
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@@ -78,11 +78,60 @@
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return results;
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}
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/**
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* Array.prototype.forEach + Array.prototype.find 版 (ES6)
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*/
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var sample_forEach = (function (findfn) {
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function eachfn (element) {
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var existingElement = this.find(findfn, element[0]);
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if (typeof existingElement !== 'undefined') {
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existingElement[1] += element[1];
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} else {
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this.push(element);
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}
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}
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return function sample_forEach (array) {
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var results = [];
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array.forEach(eachfn, results);
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return results;
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};
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}(function findfn (element) {
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return element[0] === this;
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}));
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/**
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* Array.prototype.reduce + + Array.prototype.find 版 (ES6)
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*/
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var sample_reduce = (function (findfn) {
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function reducefn (previous, current){
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var existingElement = previous.find(findfn, current[0]);
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if (typeof existingElement !== 'undefined') {
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existingElement[1] += current[1];
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} else {
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previous.push(current);
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}
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return previous;
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}
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return function sample_reduce (array) {
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return array.reduce(reducefn, []);
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}
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}(function findfn (element) {
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return element[0] === this;
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}));
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var array = [['a',10], ['b',20], ['c',30], ['a',40], ['a',50]];
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console.log(JSON.stringify(sample_indexOf(array))); // [["a",100],["b",20],["c",30]]
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console.log(JSON.stringify(sample_ObjectLiteral(array))); // [["a",100],["b",20],["c",30]]
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console.log(JSON.stringify(
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console.log(JSON.stringify(sample_map(array))); // [["a",100],["b",20],["c",30]]
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console.log(JSON.stringify(sample_forEach(array))); // [["a",100],["b",20],["c",30]]
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console.log(JSON.stringify(
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console.log(JSON.stringify(sample_reduce(array))); // [["a",100],["b",20],["c",30]]
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console.log(JSON.stringify(sample3(array))); // [["a",100],["b",20],["c",30]]
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```
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個人的には ES6 の `Map` で `map` オブジェクトを返す仕様に変更する事がお勧めです。
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@@ -93,7 +142,16 @@
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- [Object.prototype.hasOwnProperty() - JavaScript | MDN](https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty)
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- [Object.keys() - JavaScript | MDN](https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/Object/keys)
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- [Map - JavaScript | MDN](https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/Map)
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- [Array.prototype.forEach() - JavaScript | MDN](https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach)
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- [Array.prototype.reduce() - JavaScript | MDN](https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce)
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- [Array.prototype.find() - JavaScript | MDN](https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/Array/find)
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- [paulmillr/es6-shim](https://github.com/paulmillr/es6-shim)
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- [ECMAScript 6 compatibility table](http://kangax.github.io/compat-table/es6/)
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---
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**(2015/12/04 23:07追記)**
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`Array#forEach`, `Array#reduce`, `Array#find` を使ったコードを追記しました。
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Re: kado_ さん
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1
編集テスト
answer
CHANGED
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File without changes
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