JS(ES6):根据对象属性简化数组 [英] JS (ES6): Reduce array based on object attribute

问题描述

我有一个像这样的数组:

I have an array like this:

const fruits = [ 
    { fruit: 'apple',  year: 2018 },
    { fruit: 'apple',  year: 2018 },
    { fruit: 'banana', year: 2018 },
    { fruit: 'orange', year: 2018 },
    { fruit: 'apple',  year: 2017 },
    { fruit: 'apple',  year: 2016 }
];

现在，我想简化此数组，以查看每年有多少个水果以及总数.这样结果看起来像这样:

Now I want to reduce this array to see how many fruits there are each year and how much the total is. So that the result looks like this:

const result = [ 
    { year: 2018, apple: 2, banana: 1, orange: 1 total: 4 },
    { year: 2017, apple: 1, total: 1 },
    { year: 2016, apple: 1, total: 1 }
];

我尝试使用reduce，但是我不知道如何根据年份对它进行分组.也许还有lodash的助手?

I have tried with reduce, but I couldn't figure out how to group it based on the year. Maybe there is also a lodash helper?

推荐答案

使用Object.values和reduce

var output = Object.values(fruits.reduce( (a,c) => {
  a[c.year] = a[c.year] || { year : c.year };  
  a[c.year]["total"] = (a[c.year]["total"] || 0) + 1;
  a[c.year][c.fruit] = (a[c.year][c.fruit] || 0) + 1;
  return a;
},{}));

演示

var fruits = [{
    fruit: 'apple',
    year: 2018
  },
  {
    fruit: 'apple',
    year: 2018
  },
  {
    fruit: 'banana',
    year: 2018
  },
  {
    fruit: 'orange',
    year: 2018
  },
  {
    fruit: 'apple',
    year: 2017
  },
  {
    fruit: 'apple',
    year: 2016
  }
];

var output = Object.values(fruits.reduce((a, c) => {
  a[c.year] = a[c.year] || {
    year: c.year
  };
  a[c.year]["total"] = (a[c.year]["total"] || 0) + 1;
  a[c.year][c.fruit] = (a[c.year][c.fruit] || 0) + 1;
  return a;
}, {}));

console.log(output);

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