Dynamically accessing object property in .map array function

Question

i want to have reusable function that maps an array of objects based on property passed as parameter to function.

Here's my code:

let arr = [
  {
    country: 'poland',
    population: 380000
  },
  {
    country: 'bangladesh',
    population: 3492423
  }
]

function filterMyArr (myArr, condition) {
  return myArr.map(element => element.country)
}

console.log(filterMyArr(arr))

When i change code and try to pass condition, while executing it doesn't work. I want to call a function with second parameter for example filterMyArr(arr, country) and to have similar outcome. I want it to be reusable so i can use it for population or any other property. Thank you.

score 6 · Answer 1 · answered Nov 12 '18 at 12:46

6

You just need to use bracket notation, like this:

function filterMyArr (myArr, condition) {
  return myArr.map(element => element[condition])
}

Where you pass the condition as a string as a name of a property in your object.

Note:

But just be aware that calling the function without this condition argument, will throw an error, when you do:

console.log(filterMyArr(arr))

answered Nov 12 '18 at 12:46

cнŝdk

31,391
7
56
78

You can set default value of `condition` to `country` – Mohammad Nov 12 '18 at 12:55
@Mohammad Yes we can, it's one way of doing things. It depends on the logic. – cнŝdk Nov 12 '18 at 12:56

score 2 · Accepted Answer · answered Nov 12 '18 at 12:46

You were very close. Try this

let arr = [
  {
    country: 'poland',
    population: 380000
  },
  {
    country: 'bangladesh',
    population: 3492423
  }
]

function filterMyArr (myArr, condition) {
  return myArr.map(element => element[condition])
}

console.log('Countries - ', filterMyArr(arr, 'country'))

console.log('Population - ', filterMyArr(arr, 'population'))

Mohammad Usman · Answer 3 · 2018-11-12T12:49:14.940

0

You need to pass second argument (property) as a string and access it using bracket notation:

let arr = [
  {country: 'poland', population: 380000},
  {country: 'bangladesh', population: 3492423}
];

function filterMyArr (myArr, prop) {
  return myArr.map(obj => obj[prop]);
}

console.log(filterMyArr(arr, 'country'));
console.log(filterMyArr(arr, 'population'));

edited Nov 12 '18 at 12:49

answered Nov 12 '18 at 12:48

Mohammad Usman

37,952
20
92
95

Thank you. Forgot to try brackets, my bad : / – Kamil Staszewski Nov 12 '18 at 12:48

Dynamically accessing object property in .map array function

3 Answers3

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