module.exports = function transform(arr) { if (!Array.isArray(arr)) throw new Error('if arr is not an Array'); let count = 1; arr.filter(item => item === '--discard-next' || item === '--discard-prev' ? count++ : ''); for (let i = 0, len = arr.length; i < len; i++) { if (arr[i] === '--double-next') i + 1 < len ? arr[i] = arr[i+1] : arr[i] = ' '; if (arr[i] === '--double-prev') i ? arr[i] = arr[i-1] : arr[i] = ' '; } while (count--) { for (let i = 0, len = arr.length; i < len; i++) { if (arr[i] === '--discard-next' || arr[i] === '--discard-prev') { if (arr[i] === '--discard-next' && i + 1 < len) arr[i+1] = ' '; if (arr[i] === '--discard-prev' && i) arr[i-1] = ' '; arr[i] = ' '; break; } } arr = arr.filter(item => item !== ' '); } return arr; };