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分組對(duì)象數(shù)組的最有效方法

JavaScript 算法與數(shù)據(jù)結(jié)構(gòu)

回首憶惘然 2019-05-27 15:04:23

分組對(duì)象數(shù)組的最有效方法在數(shù)組中對(duì)對(duì)象進(jìn)行分組的最有效方法是什么？例如，給定此對(duì)象數(shù)組：[ { Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" }, { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" }, { Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" }, { Phase: "Phase 1", Step: "Step 2", Task: "Task 2", Value: "20" }, { Phase: "Phase 2", Step: "Step 1", Task: "Task 1", Value: "25" }, { Phase: "Phase 2", Step: "Step 1", Task: "Task 2", Value: "30" }, { Phase: "Phase 2", Step: "Step 2", Task: "Task 1", Value: "35" }, { Phase: "Phase 2", Step: "Step 2", Task: "Task 2", Value: "40" }]我在表格中顯示這些信息。我想用不同的方法分組，但我想總結(jié)這些值。我正在使用Underscore.js作為其groupby函數(shù)，這很有幫助，但并沒(méi)有完成整個(gè)技巧，因?yàn)槲也幌Ｍ鼈儭安鸱帧钡恰昂喜ⅰ?，更像是SQL group by方法。我正在尋找的是能夠總計(jì)特定值（如果要求）。所以，如果我做了groupby Phase，我想要收到：[ { Phase: "Phase 1", Value: 50 }, { Phase: "Phase 2", Value: 130 }]如果我做了分組Phase/ Step，我會(huì)收到：[ { Phase: "Phase 1", Step: "Step 1", Value: 15 }, { Phase: "Phase 1", Step: "Step 2", Value: 35 }, { Phase: "Phase 2", Step: "Step 1", Value: 55 }, { Phase: "Phase 2", Step: "Step 2", Value: 75 }]是否有一個(gè)有用的腳本，或者我應(yīng)該堅(jiān)持使用Underscore.js，然后循環(huán)結(jié)果對(duì)象自己做總計(jì)？

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3 回答

白板的微信

TA貢獻(xiàn)1883條經(jīng)驗(yàn) 獲得超3個(gè)贊

如果你想避免使用外部庫(kù)，你可以簡(jiǎn)潔地實(shí)現(xiàn)類似的vanilla版本groupBy()：

var groupBy = function(xs, key) {

return xs.reduce(function(rv, x) {

(rv[x[key]] = rv[x[key]] || []).push(x);

return rv;

}, {});

};

console.log(groupBy(['one', 'two', 'three'], 'length'));

// => {3: ["one", "two"], 5: ["three"]}

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慕姐8265434

TA貢獻(xiàn)1813條經(jīng)驗(yàn) 獲得超2個(gè)贊

使用ES6 Map對(duì)象：

function groupBy(list, keyGetter) {

const map = new Map();

list.forEach((item) => {

const key = keyGetter(item);

const collection = map.get(key);

if (!collection) {

map.set(key, [item]);

} else {

collection.push(item);

}

});

return map;

}

// example usage

const pets = [

{type:"Dog", name:"Spot"},

{type:"Cat", name:"Tiger"},

{type:"Dog", name:"Rover"},

{type:"Cat", name:"Leo"}

];

const grouped = groupBy(pets, pet => pet.type);

console.log(grouped.get("Dog")); // -> [{type:"Dog", name:"Spot"}, {type:"Dog", name:"Rover"}]

console.log(grouped.get("Cat")); // -> [{type:"Cat", name:"Tiger"}, {type:"Cat", name:"Leo"}]

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陪伴而非守候

TA貢獻(xiàn)1757條經(jīng)驗(yàn) 獲得超8個(gè)贊

與ES6：

const groupBy = (items, key) => items.reduce(
  (result, item) => ({
    ...result,
    [item[key]]: [
      ...(result[item[key]] || []),
      item,
    ],
  }), 
  {},);

反對(duì) 回復(fù) 2019-05-27