javascript - 如何在对象数组上使用 reduce 方法来创建一个具有每个对象总值的对象？

Question

我正在尝试对一组对象使用 reduce 方法，每个对象都是一个人和他们喜欢的冰淇淋口味。目标是将此数组缩减为单个对象，该对象包含作为属性的 flavor 以及作为值列出 flavor 的总次数。

数据:

const data = [
     { name: 'Tyler', favoriteIceCreams: ['Strawberry', 'Vanilla', 'Chocolate', 'Cookies & Cream'] },
     { name: 'Richard', favoriteIceCreams: ['Cookies & Cream', 'Mint Chocolate Chip', 'Chocolate', 'Vanilla'] },
     { name: 'Amanda', favoriteIceCreams: ['Chocolate', 'Rocky Road', 'Pistachio', 'Banana'] },
     { name: 'Andrew', favoriteIceCreams: ['Vanilla', 'Chocolate', 'Mint Chocolate Chip'] },
     { name: 'David', favoriteIceCreams: ['Vanilla', 'French Vanilla', 'Vanilla Bean', 'Strawberry'] },
     { name: 'Karl', favoriteIceCreams: ['Strawberry', 'Chocolate', 'Mint Chocolate Chip'] }
 ];

这是我目前所拥有的，但老实说我不确定该怎么做。

let iceCreamTotals = {
         Strawberry: 0,
         Vanilla: 0,
         Chocolate: 0,
         CookiesCream: 0,
         MintChocolateChip: 0,
         RockyRoad: 0,
         Pistachio: 0,
         Banana: 0,
         FrenchVanilla: 0,
         VanillaBean: 0
     }

     data.reduce((total, current) => {

         return iceCreamTotals
     }, 0)

Answer 1

将此数组缩减为单个对象，因此累加器(reduce 的第二个参数，可选)应该是一个对象。然后在每个步骤中计算数组中每个元素的相应属性 (c.favoriteIceCreams.forEach)。 p[cream] = (p[cream] || 0) + 1; 只是“如果存在则加一，否则设置为 0+1”的语法糖。

const data = [
     { name: 'Tyler', favoriteIceCreams: ['Strawberry', 'Vanilla', 'Chocolate', 'Cookies & Cream'] },
     { name: 'Richard', favoriteIceCreams: ['Cookies & Cream', 'Mint Chocolate Chip', 'Chocolate', 'Vanilla'] },
     { name: 'Amanda', favoriteIceCreams: ['Chocolate', 'Rocky Road', 'Pistachio', 'Banana'] },
     { name: 'Andrew', favoriteIceCreams: ['Vanilla', 'Chocolate', 'Mint Chocolate Chip'] },
     { name: 'David', favoriteIceCreams: ['Vanilla', 'French Vanilla', 'Vanilla Bean', 'Strawberry'] },
     { name: 'Karl', favoriteIceCreams: ['Strawberry', 'Chocolate', 'Mint Chocolate Chip'] }
 ];
 
 console.log(data.reduce((p, c) => {
  c.favoriteIceCreams.forEach(cream => {
    p[cream] = (p[cream] || 0) + 1;
  });
  return p;
 }, {}));