Mapped array intersection

JavaScript, Array · Oct 20, 2020

Returns the elements that exist in both arrays, after applying the provided function to each array element of both.

  • Create a Set by applying fn to all elements in b.
  • Use Array.prototype.filter() on a to only keep elements, which produce values contained in b when fn is applied to them.
const intersectionBy = (a, b, fn) => {
  const s = new Set(b.map(fn));
  return [...new Set(a)].filter(x => s.has(fn(x)));
};

intersectionBy([2.1, 1.2], [2.3, 3.4], Math.floor); // [2.1]
intersectionBy(
  [{ title: 'Apple' }, { title: 'Orange' }],
  [{ title: 'Orange' }, { title: 'Melon' }],
  x => x.title
); // [{ title: 'Orange' }]

More like this

  • JavaScript Array Set Operations

    Learn how to apply mathematical set operations to JavaScript arrays.

    Collection · 12 snippets

  • Mapped array symmetric difference

    Returns the symmetric difference between two arrays, after applying the provided function to each array element of both.

    JavaScript, Array · Oct 22, 2020

  • Mapped array difference

    Returns the difference between two arrays, after applying the provided function to each array element of both.

    JavaScript, Array · Oct 19, 2020

  • Mapped array union

    Returns every element from both arrays that exists at least once after applying the provided function.

    JavaScript, Array · Oct 22, 2020