bbo/difference_by.js

bbo is a utility library of zero dependencies for javascript.

'use strict';

/**
 * Returns the difference between two arrays,
 * after applying the provided function to each array element of both.
 */
function differenceBy(a, b, fn) {
  var s = new Set(b.map(fn));
  return a.map(fn).filter(el => !s.has(el));
}

module.exports = differenceBy;