/******************************************************************************/
'use strict';
/******************************************************************************/
class SuperArray extends Array {
  constructor(...args) {
    super(...args);
  }

  diff(comparisonArray) {
    var values = [];
    var hash = {};

    for (var i of comparisonArray) {
      hash[i] = true;
    }

    for (var i of this) {
      if (!hash[i]) {
        values.push(i);
      }
    }

    return values;
  }
}

const sa = new SuperArray(1, 2, 3);
console.log(sa.diff(['1', '2', 3]));

class SuperArray extends Array {
  diff(comparisonArray) {
    return this.filter(elem => !comparisonArray.includes(elem));
  }
}

const sa = new SuperArray(1, 2, 3);
console.log(sa.diff(['1', '2', 3]));