使用es6数组方法从数组中提取第一个对象

Question

我有以下代码来获取一个对象的数组：

let selectedShop = initialResultsState.get('products')
        .filter(product => product.shop.selected)

console.log(selectedShop)

结果：

我是否可以通过在另一操作中将另一个es6数组方法插入字符串的末尾filter而不是这样做从数组中提取对象let newVariable = selesctedShop[0]？

我试图把它串起来：

.map(x => {return { shop: x.shop, products: x.products }})

但它仍然是一个对象的数组，因为map总是返回一个新数组。

Answer 1

Two basic ways:

First way is shift'ing:

Array method, you can use Array.prototype.shift().

let selectedShop = initialResultsState.get('products')
    .filter(product => product.shop.selected)
    .shift();

Second way is an assignment:

You can do this, by destructuring assignment. In your case:

let [selectedShop] = initialResultsState.get('products')
    .filter(product => product.shop.selected);

This is available in ES6, supported in major browsers without transpiling.

但是您可能会看到另一种方法，答案是（Mikael Lennholm的答案）Array.prototype.find()。这样可以提高性能。

Answer 2

How about using the find() method instead of filter()? find() always return a single item, not wrapped in an array, unless it doesn't find any item, in which case it returns undefined

let selectedShop = initialResultsState.get('products')
    .find(product => product.shop.selected)

It's also a lot more efficient since it actually stops iterating over the array as soon as it has found an item. filter() will always iterate over the entire array which is a waste if you're only interested in the first relevant item anyway.