Comparation with Array search and Map Search

Sample code

function searchMap(a, b) { //fast
    let s = new Set()
    for (let x of a)
      if (b.has(x)) s.add(x)
    return s
}
function searchArray() { //slow
    let s = new Set()
    for (let x of a)
      for (let y of b)
        if (x == y) s.add(x)
    return s
}