arrzip/arrzip.js

Merge n number of arrays by shortest or longest array

'use strict';
module.exports = function(arr){
  function findExtremes(arr){
    var lowest = arr[0].length;
    var highest = arr[0].length;
    for (var i = 0; i < arr.length; i++) {
      if (arr[i].length < lowest) lowest = arr[i].length;
      if (arr[i].length > highest) highest = arr[i].length;
    }

    return {'lowest': lowest, 'highest': highest};
  };

  function short(arr, shortest){
    var new_arr = [];
    var tmp_arr = [];

    for (var i = 0; i < shortest; i++){
      for (var j = 0; j < args.length; j++) {
        tmp_arr.push(args[j][i]);
      }
      new_arr.push(tmp_arr);
      tmp_arr = [];
    }
    return new_arr;
  };

  function lng(arr, longest){
    var new_arr = [];
    var tmp_arr = [];

    for (var i = 0; i < longest; i++){
      for (var j = 0; j < arr.length; j++) {
        if (i < arr[j].length){
          tmp_arr.push(arr[j][i]);
        }
      }
      new_arr.push(tmp_arr);
      tmp_arr = [];
    }
    return new_arr;
  };

  var start = 0;
  var args = [];
  var singleFlag = 0;

  for (var key in arguments) {
    args.push(arguments[key]);
  };

  if (typeof args[args.length-1] === 'boolean'){
    start = args[args.length-1];
    args = args.slice(0,-1);
  }

  function allArrays(element, index, array){
    return Array.isArray(element);
  }

  if (args.length < 2){
    throw new Error('arrzip expects two arrays, got ' + args.length);
  } else if (!args.every(allArrays)) {
    throw new TypeError('Expected all arrays, didn\'t get all arrays');
  }

  var extremes = findExtremes(args.slice(0, args.length));

  if (!start) return short(args, extremes.lowest);
  else return lng(args, extremes.highest);
};