如何从Javascript中的过滤器返回特定值

Question

I have an object array

animals[
 {id:1, name:"cat"}, 
 {id:2, name:"dog"}, 
 {id:3, name:"fish"}
]

and i have another

selected = [1,2]

I want to have a return as a string of selected ones:

"cat, dog"

I currently know how to filter

   const selectedAnimals = selected.filter(function(e) {
      return animals.find(o => o.id == e);
    })

But this returns the list of ids. How would I rerturn the list of names and in string format? Would I need to use reduce or can i do it with the filter option?

Answer 1

You are using the filter function backwards. You should use filter on the animals array. Try this:

const selectedAnimals = animals.filter(function(e) {
   return selected.find(id => e.id == id);
})

This will give you a list of animal objects with ids, then you can loop over that and extract the name if you want to create an array of just the names.

Answer 2

You have to use filter() on your animals array. Can use includes() to check if array contains given value.

var selectedAnimals = animals.filter(animal => selected.includes(animal.id));

Live Example:

 var animals = [ {id:1, name:"cat"}, {id:2, name:"dog"}, {id:3, name:"fish"} ]; var selected = [1,2]; var selectedAnimals = animals.filter(animal => selected.includes(animal.id)); console.log(selectedAnimals); 

Answer 3

You can archive that by doing the following

let animals = [
 {id:1, name:"cat"}, 
 {id:2, name:"dog"}, 
 {id:3, name:"fish"}
]

let selected = [1,2]

const selectedAnimals = animals.filter(e =>(
      selected.includes(e.id))
    )

and selectedAnimals should have [ {id: 1, name: "cat"}, {id: 2, name: "dog"} ]

Alternatively, you can use a map but then you will end up with the following.

let selectedAnimals = animals.map((e,t) => { if(selected.includes(e.id)) return e.name; else return null} )

["cat", "dog", null]