How to calculate intersection of multiple arrays in JavaScript? And what does [equals: function] mean?

Question

I am aware of this question, simplest code for array intersection but all the solutions presume the number of arrays is two, which cannot be certain in my case.

I ha

Answer 1

Lodash pure:

_.keys(_.pickBy(_.groupBy(_.flatten(arrays)), function (e) {return e.length > 1}))

Lodash with plain js:

var elements = {}, duplicates = {};
 _.each(arrays, function (array) {
     _.each(array, function (element) {
         if (!elements[element]) {
             elements[element] = true;
         } else {
             duplicates[element] = true;
         }
     });
 });
_.keys(duplicates);