Itertool for js

itertools.js

// drop leading zeroes from array
// TODO: make as polyfill
// e.g. https://developer.mozilla.org/ru/docs/Web/JavaScript/Reference/Global_Objects/Array/filter#Polyfill
const dropWhile = arr => arr.reduce(
  (state, v) => (v === 0 && state.drop
    ? ({ arr: [...state.arr], drop: true })
    : ({ arr: [...state.arr, v], drop: false })), { arr: [], drop: true },
).arr;