使用Array.prototype.includes来定位对象数组中的属性

Question

With Array.prototype.includes you can do something like this:

let array1 = [1, 2, 3];

console.log(array1.includes(2)); // return true

My question is: can you use includes for an array of objects, where you want to find, say, "name" = "Jane"? Take for instance the following data:

let array2 = [{"name" : "John", age: 24}, {"name" : "Jane", age: 36}]

Is this something you can do with the includes method - and what would it look like?

Answer 1

You can use it, but only if you have the reference to the object ( not its structural equivalent).

const o1 = { name: '1' }
const o2 = { name: '2' }
const arr = [o1, o2]
arr.includes(o1) // true
arr.includes({ name: '1' }) // false

This is because includes uses the "SameValueZero" algorithm, as per the spec (emphasis mine):

includes compares searchElement to the elements of the array, in ascending order, using the SameValueZero algorithm , and if found at any position, returns true ; otherwise, false is returned.

" SameValueZero " will always return false for different references, hence the second attempt from the code above will return false .

You can use Array#some instead, which lets you specify a lambda as the parameter. Then you can write your custom equality logic even for objects.

arr.some(o => o.name == '1') // true

From your comment , I see you're interested in checking against multiple values. You can simply use the || operator with some in this case:

arr.some(o => o.name == '1' || o.name == '2' || o.name == '3')

If you do not wish to specify all of them like this, you can do something like the following.

arr.some(o => ['1', '2', '3'].includes(o.name))

Answer 2

In that case you could use some method instead and it will return true on first match.

 let array = [{"name" : "John", age: 24}, {"name" : "Jane", age: 36}] let check = array.some(({name}) => name == 'Jane'); console.log(check) 

Answer 3

  array.find(user => user.name === "Jane")

As objects get compared by reference, .includes doesn't help you in most cases, then you have to through all elements manually and check for equality, thats what .find does. It either returns the found user or undefined . If you just need a boolean use .some that works like .find but either returns true or false.

Answer 4

You can do this.

 let array2 = [{ "name": "John", age: 24 }, { "name": "Jane", age: 36 }] var some = array2.some((i) => { return i.name === 'Jane' }) var map = array2.map((i) => { return i.name === 'Jane' }) console.log('some', some) console.log('map', map)