how to find difference between two array using lodash/underscore in nodejs

Question

I have two arrays of arrays and am trying to find the difference.

var a = [[ 11, 24, 28, 38, 42, 44 ],
  [ 7, 19, 21, 22, 29, 38 ],
  [ 2, 21, 27, 30, 33, 40 ],
  [ 6, 11, 12, 21, 34, 48 ],
  [ 1, 10, 17, 31, 35, 40 ],
  [ 1, 18, 26, 33, 36, 45 ],
  [ 15, 21, 22, 24, 38, 46 ],
  [ 5, 17, 21, 27, 29, 41 ],
  [ 3, 7, 12, 16, 20, 28 ],
  [ 9, 12, 13, 18, 30, 37 ],
  [ 3, 19, 21, 31, 33, 46 ],
  [ 6, 11, 16, 18, 20, 34 ],
  [ 1, 3, 11, 13, 24, 28 ],
  [ 12, 13, 16, 40, 42, 46 ],
  [ 1, 3, 5, 36, 37, 41 ],
  [ 14, 15, 23, 24, 26, 31 ],
  [ 7, 13, 14, 15, 27, 28 ]];

var b = [[ 4, 7, 9, 21, 31, 36 ],
  [ 2, 5, 6, 12, 15, 21 ],
  [ 4, 7, 8, 15, 38, 41 ],
  [ 11, 24, 28, 38, 42, 44 ],
  [ 7, 19, 21, 22, 29, 38 ]];

How would I find:

c = [[ 2, 21, 27, 30, 33, 40 ],
  [ 6, 11, 12, 21, 34, 48 ],
  [ 1, 10, 17, 31, 35, 40 ],
  [ 1, 18, 26, 33, 36, 45 ],
  [ 15, 21, 22, 24, 38, 46 ],
  [ 5, 17, 21, 27, 29, 41 ],
  [ 3, 7, 12, 16, 20, 28 ],
  [ 9, 12, 13, 18, 30, 37 ],
  [ 3, 19, 21, 31, 33, 46 ],
  [ 6, 11, 16, 18, 20, 34 ],
  [ 1, 3, 11, 13, 24, 28 ],
  [ 12, 13, 16, 40, 42, 46 ],
  [ 1, 3, 5, 36, 37, 41 ],
  [ 14, 15, 23, 24, 26, 31 ],
  [ 7, 13, 14, 15, 27, 28 ]];

I had tried underscore:

_ = require('underscore');
_.difference(a,b);

But it doesn't work.

I also tried lodash:

_ = require('lodash');
_.differenceBy(a,b);

but it doesn't work either.

What am I doing wrong here?

Answer 1

Use _.differenceWith, and pass a comparator which compares two arrays, as in:

_.differenceWith(a, b, _.isEqual);