Best way to remove common object from object array in Javascript

Question

I have followings object array

a = [{c:1, r:2}, {c:2, r:2}, {c:3, r:2}]
b = [{c:1, r:1}, {c:2, r:2}, {c:3, r:3}]

Now I want to remove common object this,

Like var result = removeCommon(a, b);
Output result = [{c:1, r:2}, {c:2, r:2}, {c:3, r:2}, {c:1, r:1}, {c:3, r:3}]

I need best way as array size is big

possible duplicate of [Simplest code for array intersection in javascript](http://stackoverflow.com/questions/1885557/simplest-code-for-array-intersection-in-javascript) — Naeem Shaikh, Jan 08 '15 at 14:05
yes the accepted answer in that question is the best one! :) — Naeem Shaikh, Jan 08 '15 at 14:07
as shown, none of those objects are actually common between arrays. you have to match only by value, and that's going to be really messy and long-winded. — dandavis, Jan 08 '15 at 14:08
@NaeemShaikh : Solution given by assuming it is already sorted, but here it is not — Urvish, Jan 08 '15 at 14:09
@asimes: sure, but those two indentical-key+value objects are indeed not the same, and JS has no object-by-val comparision operator, only compare by ref, and they are not the same ref. so you need to serialize, or over-iterate to compare. it's one of the worst things about JS, but there's no easy answer... — dandavis, Jan 08 '15 at 14:11
@NaeemShaikh : I dont want to sort, I just want to remove common — Urvish, Jan 08 '15 at 14:11
@Qantas94Heavy : as in the code above I want the result ehich does not have {c:2, r:2} which is duplicate — Urvish, Jan 08 '15 at 14:13
@Urvish: let me rephrase. Would you call `{c:2,r:2}` and `{c:2,r:2,z:2}` duplicates for the purpose of your code? — Qantas 94 Heavy, Jan 08 '15 at 14:15
if the objects come from the same place and are indeed the same objects, any Array.uniuqe routine will work. if the objects are consistent in key-order, then you can compare the JSON.stringify() version of each to find duplicates via string compares (at least for now). — dandavis, Jan 08 '15 at 14:15
This question seems to be asking for union (without duplicates), not intersection — Paul S., Jan 08 '15 at 14:16
Solution is _.uniq(a.concat(b), function(array){ return "c:" + array.c + "r:" + array.r; }) — Urvish, Jan 08 '15 at 14:18

score 2 · Answer 1 · answered Jan 08 '15 at 14:20

2

I found the work around

_.uniq(a.concat(b), function(array){
    return "c:" + array.c + "r:" + array.r;
})

result : [{c:1, r:2}, {c:2, r:2}, {c:3, r:2}, {c:1, r:1}, {c:3, r:3}]

answered Jan 08 '15 at 14:20

Urvish

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yeah, but what about for {a:1,b:4} or {id:45432, total: 765} ? – dandavis Jan 08 '15 at 14:21
Looks like [Lo-Dash](https://lodash.com/docs#uniq) or [Underscore](http://underscorejs.org/#uniq), both have the same function signature (except Lo-Dash has an optional `thisArg`). – Qantas 94 Heavy Jan 08 '15 at 16:29

score 2 · Answer 2 · answered Jan 08 '15 at 14:29

My solution (without external libraries):

var a = [{c:1, r:2}, {c:2, r:2}, {c:3, r:2}];
var b = [{c:1, r:1}, {c:2, r:2}, {c:3, r:3}];
var c = removeCommon(a, b);

console.log(c);

function removeCommon(a, b) {
  var result = {};

  a.concat(b).forEach(function (i) {
    result['c' + i.c + 'r' + i.r] = i;
  });

  return Object.keys(result).map(function (k) {
    return result[k];
  });
}

And a fiddle.

Best way to remove common object from object array in Javascript

2 Answers2