hexlet-braingames-by-mput/src/games/progressionGame.js

Learning Hexlet.io node.js project implementation.

import { cons } from 'hexlet-pairs';
import newGame from '..';
import randomInt from '../utils';

const description = 'What number is missing in this progression?';

const getQueAndAnsw = () => {
  const progElementsCount = 10;
  const skippedElmPos = randomInt(10) - 1;
  const firstElm = randomInt(10);
  const step = randomInt(5);

  const iterQnA = (currentElem, currentElmPos, progression, hiddenElm) => {
    if (currentElmPos === progElementsCount) {
      return cons(progression, hiddenElm);
    }
    const nextElm = currentElem + step;
    const nextElmPos = currentElmPos + 1;
    const separator = (currentElmPos === 0) ? '' : ' ';

    if (currentElmPos === skippedElmPos) {
      return iterQnA(nextElm, nextElmPos, `${progression}${separator}..`, String(currentElem));
    }
    return iterQnA(nextElm, nextElmPos, `${progression}${separator}${currentElem}`, hiddenElm);
  };

  return iterQnA(firstElm, 0, '', '');
};

export default () => newGame(description, getQueAndAnsw);