如果已知对象的其他属性，该如何返回该对象的属性？

Question

I have array of objects with unique names:

let arr = [
  {
    'name':'B',
    'id': 1
  },
  {
    'name': 'c',
    'id': 12
    },
  {
    'name': 'a',
    'id': 13
  }
]

How can I get id if I know the name . For example I have B and it need to return 1 ?

My solution :

const foo = (arr, name) => arr.filter(el => el.name === name)[0].id

foo(arr, 'B') // 1

Hope there is a better solution to this problem

Answer 1

You should use Array.prototype.find() instead of Array.prototype.filter() , because .find() returns only the first matching element of the array - .filter() returns all matching elements. Your code should look like this:

const foo = (arr, name) => arr.find(el => el.name == name).id;

Working snippet:

 let arr = [ { 'name': 'B', 'id': 1 }, { 'name': 'c', 'id': 12 }, { 'name': 'a', 'id': 13 } ] const foo = (arr, name) => arr.find(el => el.name == name).id; var theID = foo(arr, 'B'); console.log(theID); 

Answer 2

Array.prototype.find is fine for few lookups if you don't mind that it's not supported in IE, and that it can result in error if the item is not found. For multiple lookups, I recommend making a lookup object :

 const arr = [ { name:'B', id: 1 }, { name: 'c', id: 12 }, { name: 'a', id: 13 } ] const obj = arr.reduce((o, v) => (o[v.name] = v.id, o), {}) console.log( obj['B'] ) // 1 console.log( obj['A'] ) // undefined 

---

If by any chance the data is from JSON.parse :

 const obj = {}, json = '[{"name":"B","id":1},{"name":"c","id":12},{"name":"a","id":13}]' JSON.parse(json, (k, v) => v.name ? (obj[v.name] = v.id) : v) console.log( obj['B'] ) // 1 console.log( obj['A'] ) // undefined