How to get filtered array with defineProperty JS?

Question

I've tried looking for a way of doing it but found none.

I want to filter out array items when I'm accessing the array. For example: filter out only negative values

let arr = [-1, -2, -4, -5, 8, 9, 10, -7, 5, 7, 8, 4, -12];
let o = {
  arr: arr
};

Object.defineProperty(o, 'arr', {
  get: () => { /* filter only negative values */ }
});

// should print only positive values
console.log(o.arr)

ptothep · Accepted Answer · 2021-01-15T11:24:53.260

2

You can use filter

let arr = [-1, -2, -4, -5, 8, 9, 10, -7, 5, 7, 8, 4, -12];
let o = {
  array: arr
};

Object.defineProperty(o, 'arr', {
  get: () => {
    return o.array.filter(a => a >= 0)
  }
});

console.log(o.arr)

edited Jan 15 '21 at 11:24

answered Jan 15 '21 at 11:17

ptothep

415
3
10

And what if I dont have pointer to the array? – Omri Attiya Jan 15 '21 at 11:18
Im not sure how you could not have a pointer to it. Please explain more – ptothep Jan 15 '21 at 11:20

score 1 · Answer 2 · answered Jan 15 '21 at 11:25

you can use Array.prototype.filter and this(context)

let arr = [-1, -2, -4, -5, 8, 9, 10, -7, 5, 7, 8, 4, -12];
let o = {
  arr,
};

Object.defineProperty(o, 'negative', {
  // return array values where item < 0
  get: function () {return this.arr.filter(item => item < 0)}
});

// should print only positive values
console.log(o.negative)

How to get filtered array with defineProperty JS?

2 Answers2