Code for https://github.com/mykeels/prime-cluster

index.js

const express = require('express')
const isPrime = require('./is-prime')
const app = express()

app.get('/', (req, res) => {
    const primes = []
    const max = Number(req.query.max) || 1000
    for (let i = 1; i <= max; i++) {
        if (isPrime(i)) primes.push(i)
    }
    res.json(primes)
})

app.listen(process.env.PORT || 3030)

console.log('app is running!')

module.exports = app

is-prime.js

module.exports = (num) => {
    if ([2, 3].indexOf(num) >= 0) return true;
    else if ([2, 3].some(n => num % n == 0)) return false;
    else {
        let i = 5, w = 2;
        while ((i * i) <= num) {
            if (num % i == 0) return false
            i += w
            w = 6 - w
        }
    }
    return true
}

package.json

{
  "name": "prime-cluster",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node index"
  },
  "author": "",
  "license": "MIT",
  "dependencies": {
    "express": "^4.16.2"
  }
}