Given two Arrays, return an Array consisting only of the non-intersecting items

Question

I'm getting stacked in an issue in JavaScript.

I have two arrays and I want to check if they intersect on some elements then delete those elements and return new array without the intersected elements.

example :

Array A ( 
[0] => 0 [1] => 1 
)

Array B ( 
[0] => 2 [1] => 1 
)

I want to check them and return:

 Array result ( 
[0] => 0 [1] => 2 
)

How can i do this in JavaScript?

http://stackoverflow.com/questions/1885557/simplest-code-for-array-intersection-in-javascript — Gerry, Sep 13 '11 at 14:58
thx for the response but this question is about returning an array with intersected elements . i want to delete them and return the rest in a new array — sken boy, Sep 13 '11 at 15:02

score 9 · Accepted Answer · edited Oct 01 '17 at 11:55

9

Checkout the library underscore.js.

Say you have two arrays,

var a = [1, 2];
var b = [2, 3];

First find the union.

var all = _.union(a, b);

Then find the intersection.

var common = _.intersection(a, b);

The final answer should be the difference between the union, and the intersection.

var answer = _.difference(all, common)

edited Oct 01 '17 at 11:55

Robert

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answered Sep 13 '11 at 15:12

Anurag

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2

+1 [Working example.](http://jsbin.com/ayujef/edit#javascript,live) Probably safe to assume that underscore code is acceptable since jQuery is apparently already loaded. – user113716 Sep 13 '11 at 15:27
Thanks for the working example - looks great :) .. Underscore is similar to jQuery in philosophy and the size isn't too big either, but it all depends on OP's requirements. – Anurag Sep 13 '11 at 15:51

Joe · Answer 2 · 2011-09-13T15:44:04.050

5

Using Array.filter, Array.lastIndexOf, and Array.indexOf:

var array1 = [1,2,3,4,5];
var array2 = [2,3];
var unique = array1.concat(array2)
                   .filter(function (item, index, array) {
                       return array.indexOf(item) == array.lastIndexOf(item);
                   })

Neither method is 100% cross browser by default, but both links having safe shims for IE <= 8

edited Sep 13 '11 at 15:44

answered Sep 13 '11 at 15:05

Joe

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thanks abstractdownvotefactor, the arrays are stocked in a var and dont know ther indexes neither the elements . – sken boy Sep 13 '11 at 15:07
This won't give you elements in `array2` that don't appear in `array1`. OP's example seems to suggest that all unique values are retained. – user113716 Sep 13 '11 at 15:16
This will have a different result if you started filtering out from `array2`. The contents are both the arrays are unknown. – Anurag Sep 13 '11 at 15:16
Good improvement and an interesting solution, but just one nitpick is that you're not retaining the result (since `.filter()` returns a new Array). Perhaps just chain the `.filter()` off the `.concat()`. `var a = array1.concat(array2).filter(function (...` *EDIT:* +1 though. – user113716 Sep 13 '11 at 15:40

Blazemonger · Answer 3 · 2011-09-13T15:26:49.457

2

Well, since you specified jQuery, try this:

var arr1 = [2, 3, 4];
var arr2 = [1, 2, 3];

var arr3 = $.merge($.grep(arr1, function(el, idx) {
    return $.inArray(el, arr2) > -1;
}, true), $.grep(arr2, function(el, idx) {
    return $.inArray(el, arr1) > -1;
}, true));

alert(arr3);

It's probably not very efficient, but it's relatively concise.

edited Sep 13 '11 at 15:26

answered Sep 13 '11 at 14:58

Blazemonger

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thankx for the response but how can i implement this and return an array without the intersected elements ??? – sken boy Sep 13 '11 at 15:03

score 0 · Answer 4 · edited May 21 '17 at 10:11

0

Plain js solution, not as efficient as when jQuery is used:

function filter(a1, a2){
  var result = [];
  for(i in a1){
    exists = false;
    for(j in a2){
      if(a1[i] == a2[j])
        exists = true;
    }
    if(exists== false){
      result.push(a1[i]);
    }
  }
  return result;
}

var arr1 = [1,2,3,4,5];
var arr2 = [4,5,6,7,8];
var result1 = filter(arr1, arr2);
var result2 = filter(arr2, arr1);

var result = result1.concat(result2);

edited May 21 '17 at 10:11

Kir Chou

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answered Sep 13 '11 at 15:31

mooglife

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You really shouldn't use `for-in` on an Array *(in JavaScript)*. – user113716 Sep 13 '11 at 15:45
i finally used underscore plugin and the code of @anurag. thank you for the help – sken boy Sep 13 '11 at 15:46
@patrick dw: agreed that for-in shouldn't be used in javascript where order of parsing the elements are important. Thats the only drawback of it, me thinks. – mooglife Sep 13 '11 at 17:37
Well, it also forces you to use `.hasOwnProperty()` if you use any code that extends `Array.prototype` (which can be very useful). For Array iteration, an index-based `for` statement will be better than the more general `for-in` enumerator. – user113716 Sep 13 '11 at 17:43

Given two Arrays, return an Array consisting only of the non-intersecting items

4 Answers4