getCommonElements https://codereview.stackexchange.com/questions/96096/find-common-elements-in-a-list-of-arrays

getCommonElements.js

var arrays  = [
    [1, 4, 6, 78, 8, 9, 124, 44],
    [44, 6, 9],
    [124, 44, 16, 9]
];
function getCommonElements(arrays){//Assumes that we are dealing with an array of arrays of integers
  var currentValues = {};
  var commonValues = {};
  for (var i = arrays[0].length-1; i >=0; i--){//Iterating backwards for efficiency
    currentValues[arrays[0][i]] = 1; //Doesn't really matter what we set it to
  }
  for (var i = arrays.length-1; i>0; i--){
    var currentArray = arrays[i];
    for (var j = currentArray.length-1; j >=0; j--){
      if (currentArray[j] in currentValues){
        commonValues[currentArray[j]] = 1; //Once again, the `1` doesn't matter
      }
    }
    currentValues = commonValues;
    commonValues = {};
  }
  return Object.keys(currentValues).map(function(value){
    return parseInt(value);
  });
}
console.log(getCommonElements(arrays)); //Prints [9,44]