Chris Jarling

Lodash

Use _.intersection(): https://lodash.com/docs/4.17.15#intersection

_.intersection([2, 1], [2, 3])
// => [2]

Vanilla Javascript

Using Set

function intersection(a, b) {
  const setA = new Set(a)
  return b.filter((value) => setA.has(value))
}

Source: https://stackoverflow.com/a/73246941/4181679

Using .filter() and .includes()

const filteredArray = array1.filter((value) => array2.includes(value))

Source: https://stackoverflow.com/a/1885569/4181679

Benchmarks

100.000 runs with two arrays of 300 items each, 100 intersecting:

lodash: 1.208s
set: 826.824ms
filterIncludes: 3.765s

100.000 runs with two arrays of 3000 items each, 1000 intersecting:

lodash: 19.260s
set: 11.786s
filterIncludes: 5:37.872 (m:ss.mmm)

Which one to use?

Raw speed would indicate using Set(). However, there are other factors that play into that.

If lodash is already present in the project, I would argue for going with intersection for a few reasons:

1. Improved readability. Function name describes exactly what is happening. Could also just move e.g. Set() into a function to have the same advantages. See 2.
2. Code will likely be more maintained if its coming from lodash compared to when it's somewhere in a private codebase

If speed is essential, there will probably be a culture in the codebase that forbids using lodash anyways.