es6.js

// Search an array for nested arrays and inline them
const flatten = (arr, out = []) => {
  arr.forEach(val => {
    if (val == null) return
    if (Array.isArray(val)) flatten(val, out)
    else out.push(val)
  })
  return out
}

// Map an array and flatten it
const flatMap = (arr, mapper) => flatten(arr.map(mapper))

// Filter an array to remove the given values
const without = (arr, ...args) => arr.filter(val => !args.includes(val))