显示一本书的平均价格

Question

我需要一些代码，实现计算图书的平均价格，罗马类型。类型字段可以以任何大小写形式写入(罗马、罗马)。

let books = [
    { name: 'Some-1', author: 'Puskin', type: 'roman', price: 204.5 },
    { name: 'Some-2', author: 'Tolstoy', type: 'ROMAN', price: 321.0 },
    { name: 'Some-3', author: 'Pero', type: 'tale', price: 211.0 },
    { name: 'Some-4', author: 'Koelyo', type: 'roman', price: 204.5 },
    { name: 'Some-5', author: 'Christie', type: 'Roman', price: 245.5 },
    { name: 'Some-6', author: 'Hohol', type: 'tale', price: 366.0 }
];

所以我用这个方法派生了所有类型：

const getType = books.map(({type}) => type.toLowerCase())

此外，我的问题是，我不知道如何获得价格

Answer 1

有几种方法可以做到这一点

您可以遍历数组并对其中的所有价格求和，然后对其长度进行除法运算，还可以使用.toLowerCase()检查当前对象类型是否等于roman

如果想要返回自然数，可以使用.toFixed()方法

For循环

​

let books = [
    { name: 'Some-1', author: 'Puskin', type: 'roman', price: 204.5 },
    { name: 'Some-2', author: 'Tolstoy', type: 'ROMAN', price: 321.0 },
    { name: 'Some-3', author: 'Pero', type: 'tale', price: 211.0 },
    { name: 'Some-4', author: 'Koelyo', type: 'roman', price: 204.5 },
    { name: 'Some-5', author: 'Christie', type: 'Roman', price: 245.5 },
    { name: 'Some-6', author: 'Hoho', type: 'tale', price: 366.0 }
 ]
 
let TotalPrice = 0;
let romanPriceLength = 0;

for (let i = 0; i < books.length; i++) {
  if ((books[i].type).toLowerCase() === "roman") {
    TotalPrice += books[i].price
    romanPriceLength++
  }
}

console.log(TotalPrice / romanPriceLength)
console.log((TotalPrice / romanPriceLength).toFixed(0))

​

forEach()

​

let books = [
    { name: 'Some-1', author: 'Puskin', type: 'roman', price: 204.5 },
    { name: 'Some-2', author: 'Tolstoy', type: 'ROMAN', price: 321.0 },
    { name: 'Some-3', author: 'Pero', type: 'tale', price: 211.0 },
    { name: 'Some-4', author: 'Koelyo', type: 'roman', price: 204.5 },
    { name: 'Some-5', author: 'Christie', type: 'Roman', price: 245.5 },
    { name: 'Some-6', author: 'Hoho', type: 'tale', price: 366.0 }
 ]


let TotalPrice = 0;
let romanPriceLength = 0;

 books.forEach(book => {
  if((book.type).toLowerCase() === "roman"){
    TotalPrice += book.price
    romanPriceLength ++
  }
 })
 
 console.log(TotalPrice / romanPriceLength)
 console.log((TotalPrice / romanPriceLength ).toFixed(0))

​

为了..。的

​

let books = [
    { name: 'Some-1', author: 'Puskin', type: 'roman', price: 204.5 },
    { name: 'Some-2', author: 'Tolstoy', type: 'ROMAN', price: 321.0 },
    { name: 'Some-3', author: 'Pero', type: 'tale', price: 211.0 },
    { name: 'Some-4', author: 'Koelyo', type: 'roman', price: 204.5 },
    { name: 'Some-5', author: 'Christie', type: 'Roman', price: 245.5 },
    { name: 'Some-6', author: 'Hoho', type: 'tale', price: 366.0 }
 ]

let romanPriceLength = 0;
let TotalPrice = 0;

for(let book of books){
  if(book.type.toLowerCase() === "roman"){
    TotalPrice += book.price
    romanPriceLength++
  }
}

console.log(TotalPrice / romanPriceLength)
console.log((TotalPrice / romanPriceLength).toFixed(0))

​

Answer 2

使用for循环或forEach()来获取价格和计数的总和。

​

let books = [
    { name: 'Some-1', author: 'Puskin', type: 'roman', price: 204.5 },
    { name: 'Some-2', author: 'Tolstoy', type: 'ROMAN', price: 321.0 },
    { name: 'Some-3', author: 'Pero', type: 'tale', price: 211.0 },
    { name: 'Some-4', author: 'Koelyo', type: 'roman', price: 204.5 },
    { name: 'Some-5', author: 'Christie', type: 'Roman', price: 245.5 },
    { name: 'Some-6', author: 'Hoho', type: 'tale', price: 366.0 }
]

let TotalPrice = 0;
let count = 0;

books.forEach(book => {
  if (book.type.toLowerCase() == 'roman') {
    TotalPrice += book.price;
    count++;
  }
});

console.log((TotalPrice / books.length).toFixed(2))

​

Answer 3

你也可以用filter和reduce做到这一点：

​

let books = [
    { name: 'Some-1', author: 'Puskin', type: 'roman', price: 204.5 },
    { name: 'Some-2', author: 'Tolstoy', type: 'ROMAN', price: 321.0 },
    { name: 'Some-3', author: 'Pero', type: 'tale', price: 211.0 },
    { name: 'Some-4', author: 'Koelyo', type: 'roman', price: 204.5 },
    { name: 'Some-5', author: 'Christie', type: 'Roman', price: 245.5 },
    { name: 'Some-6', author: 'Hoho', type: 'tale', price: 366.0 }
]

const romans = books.filter(book => book.type.toLowerCase() == 'roman') 
const romansTotalPrice = romans.reduce((a, {price}) => a + price, 0)
const romansAvaragePrice = (romansTotalPrice / romans.length).toFixed(2);
console.log(romansAvaragePrice)

​