The Sieve of Eratosthenes in Javascript

erato.js

function erato(n){
  let map = new Map((new Array(n-1).fill(1)).map((n,i)=>[i+2,true]));
  for (let i = 2; i <= Math.sqrt(n);i++){
    if (!map.get(i)) continue
    for (let j = i*2; j <= n; j += i) map.set(j,false)
  }
  return Array.from(map).filter(([n,b])=>b).map(([n])=>n);
}

console.log(erato(100))