如何在JavaScript中將平面數組排序爲[鍵，數組]數組？

-1

我有一個平坦的列表，像這樣：如何在JavaScript中將平面數組排序爲[鍵，數組]數組？

[ 
{year: 2017, value: 1 }, 
{year: 2017, value: 2 }, 
{year: 2017, value: 3 }, 
{year: 2018, value: 1 }, 
{year: 2018, value: 2 }, 
{year: 2018, value: 3 }, 
{year: 2019, value: 1 }, 
]

等。

我想重組這樣的：

[ 
{year: 2017, values: [1, 2, 3] }, 
{year: 2018, values: [1, 2, 3] }, 
{year: 2019, values: [1] }, 
]

甚至

{ 
    "2017": [1, 2, 3], 
    "2018": [1, 2, 3], 
    "2019": [1] 
}

我我只是想每年獲得一個數組。我怎麼能做到這一點？

來源

2017-03-08 rball

好了，廢話。我四處搜尋，但似乎確實如此。 – rball

完整的解決方案，那麼：

var aY=[ 
    {year: 2017, value: 1 }, 
    {year: 2017, value: 2 }, 
    {year: 2017, value: 3 }, 
    {year: 2018, value: 1 }, 
    {year: 2018, value: 2 }, 
    {year: 2018, value: 3 }, 
    {year: 2019, value: 1 } 
]; // your example 
var oYs= {}; // the new structure 
for(var i= 0; i < aY.length; i++){ 
    var y= aY[i].year; 
    if (oYs[y]==null){ 
    oYs[y]= []; // create a new array of values 
    } 
    oYs[y].push(aY[i].value); // append the new value 
}

來源

2017-03-08 19:00:51 Koen

-3

這會更容易些：

{ 
    "2017": [1, 2, 3], 
    "2018": [1, 2, 3], 
    "2019": [1] 
}

來源

2017-03-08 18:50:27 Koen

好的，當然。如果數據結構可能發生變化，那麼也可以。你會怎麼做？ – rball

例如：obj [「2017」] = [「1」]然後obj [「2017」]。push（「2」）等 – Koen

請僅在實際答案中使用* Post answer *按鈕。 –

這裏是一個解決方案：

const a = [ 
    {year: 2017, value: 1 }, 
    {year: 2017, value: 2 }, 
    {year: 2017, value: 3 }, 
    {year: 2018, value: 1 }, 
    {year: 2018, value: 2 }, 
    {year: 2018, value: 3 }, 
    {year: 2019, value: 1 } 
] 

// you can take advantage of the famous Array.reduce method. 
// object solution 
const b = a.reduce(function(prev,current){ 
    if(prev[current.year]){ 
    // if the key already exists, it means we should push 
    prev[current.year].push(current.value) 
    }else{ 
    // if the key does't exist, create it and add the value to an empty array 
    prev[current.year] = [current.value]; 
    } 

    return prev; 

},{}) 
console.log(b); // { '2017': [ 1, 2, 3 ], '2018': [ 1, 2, 3 ], '2019': [ 1 ] } 

// array solution(it is kind of dependant on the previous solution) 
const c = [] 
for (key in b){ 
    if(b.hasOwnProperty(key)){ 
    c.push({year:key,value:b[key]}); 
    } 
} 
console.log(c); // [ { year: '2017', value: [ 1, 2, 3 ] }, { year: '2018', value: [ 1, 2, 3 ] }, { year: '2019', value: [ 1 ] } ]

來源

2017-03-08 19:02:58 Ismail

哦拍，這也看起來很棒。 – rball

如果你想返回一個對象作爲結果你可以簡單地使用reduce()。

var data = [ 
 
{year: 2017, value: 1 }, 
 
{year: 2017, value: 2 }, 
 
{year: 2017, value: 3 }, 
 
{year: 2018, value: 1 }, 
 
{year: 2018, value: 2 }, 
 
{year: 2018, value: 3 }, 
 
{year: 2019, value: 1 }, 
 
] 
 

 
var result = data.reduce(function(r, e) { 
 
    if(!r[e.year]) r[e.year] = [] 
 
    r[e.year].push(e.value) 
 
    return r 
 
}, {}) 
 

 
console.log(result)

來源

2017-03-08 19:06:08

如何在JavaScript中將平面數組排序爲[鍵，數組]數組？

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