如何映射和减少对象数组？ [英] How to map and reduce over an array of objects?

问题描述

如何从以下对象数组中统计价格：

How do I count the prices together from the following array of objects:

const cars = [
{
    price: 10000,
    car: 'audi'
},
{
    price: 10000,
    car: 'audi'
},
{
    price: 10000,
    car: 'nissan'
},
{
    price: 10000,
    car: 'nissan'
},
{
    price: 20000,
    car: 'mazda'
},
{
    price: 10000,
    car: 'nissan'
},
];

这样我就可以获得一系列对象，总价格为：

So that I would get an array of objects, with the total prices:

const cars = [
{
    price: 20000,
    car: 'audi'
},
{
    price: 30000,
    car: 'nissan'
},
{
    price: 20000,
    car: 'mazda'
}
];

尝试映射数组，然后减少，但我如何保留结构，以便我找回了一系列物品？这是不正确的：

Tried to map over the array, and then reduce, but how do i keep the structure, so that I get back an array of objects? This is incorrect:

 const newCarsArray = cars.map(item => {
     return(
        //cars.reduce ?
     )
 });

推荐答案

您可以将阵列缩小为汽车键入的对象持有总数，那么将其转换回格式非常简单

You can reduce your array to an object keyed by car, holding the total, then it's pretty simple to convert that back to your format

const cars = [{price: 10000, car: 'audi'},{price: 10000, car: 'audi'},{price: 10000, car: 'nissan'},{price: 10000, car: 'nissan'}, {price: 20000,        car: 'mazda'}, {price: 10000, car: 'nissan'}];

var map = cars.reduce((map, car) => {
  map[car.car] = map[car.car] ? map[car.car] + car.price : car.price;
  return map;
}, {});

console.log(map); // {audi: 20000, nissan: 30000, mazda: 20000}

var array = Object.keys(map).map( car => ({car: car, price: map[car]}));

console.log(array);

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