Symmetric Difference -- JavaScript -- Free Code Camp

**Symmetric Difference** -- Finding the symmetric difference of 2 or more sets of numbers. Uses `reduce()` and 2 helper functions.

[dandyandy]

Hey Stephen! Thanks for the videos, it's been great to see someone else work through the challenges to get another perspective! This was my solution:

function filter(x, y){
  var one= x.filter(function(e){return this.indexOf(e)<0;}, y);
  var two = y.filter(function(e){return this.indexOf(e)<0;}, x);
  return one.concat(two);
}
function sym(args) {
  var array = filter(arguments[0], arguments[1]);
  if(arguments.length > 2){
    for(var i = 2; i < arguments.length; i ++){
      array = filter(array, arguments[i]);
    }
    return array.reduce(function(x, y){
    if (x.indexOf(y) < 0 ) x.push(y);
    return x;
  }, []);
   
  }
  else return array;
}sym([1, 1, 2, 5], [2, 2, 3, 5], [3, 4, 5, 5]);

[PhilippeVaillancourt]

Pretty cool solution. I went a different route and used Sets. Converting the arguments to sets has the advantage of automatically removing duplicate values. Here is my code:

function sym(args) {
var setA = new Set();
var setB = new Set();

function checkIfHas(element) {
if (setA.has(element)) {
setA.delete(element);
} else {
setA.add(element);
}
}

for (var i = 0; i < arguments.length; i++) {
setB = new
}

return Array.from(setA);
}

[PhilippeVaillancourt]

+Stephen Mayeux when converting the arguments to an array, why use instead of Array.from(arguments) ?

[dajonline]

I don't understand how taking out duplicates causes the function to work. It would seem that it would change the dynamic of the array and bring up the wrong result. For example:
[1, 2, 3, 4, 4], [4, 5, 6, 7] I would think would come out to [1, 2, 3, 4, 5, 6, 7] as the extra 4 would stay. Taking out duplicates would give change it to [1, 2, 3, 4], [4, 5, 6, 7] I would think would result in [1, 2, 3, 5, 6, 7] the 4 being removed since it is in both only once. What am I missing?

[alexlopez]

Hey Stephen, you don't have a tutorial for "Record Collection"? is between "Validate US Telephone Numbers" and "Symmetric Difference" on freecodecamp.

[paolo-]

hey stephen, i tried this approach from your solution on the difference of 2 arrays test as i'm trying to solve it and it only works on 2 arrays, what you think is missing on the code below?

var i;
var argArr = [];
var oneArr;
var newArr = [];

if(Array.isArray(args)){
for(i in arguments){
argArr.push(arguments[i]);
}
}

oneArr = argArr.reduce(function (a, b) {
return a.concat(b);
});

oneArr.filter(function(value, index, array){
&& oneArr.slice(0, index).indexOf(value)==-1){
newArr.push(value);
}
});

return newArr.sort();

[dajonline]

There is no Wiki in the Symmetric Difference Free Code Camp page now.

[LexNihilus]

I used Array.prototype.includes() method and also added a second Boolean condition " &&
newArr.includes(array1[i]) === false) " in my function that creates the symmetric diff between two arrays in order to avoid adding a third "removeDupes" function.


function sym(args) {


args = Array.from(arguments);

return args.reduce(function(accumulator, currentValue ){
return diffArray(accumulator, currentValue);

});

}

function diffArray(arr1, arr2) {
var newArr =[];

function checkDiff(array1, array2){

for(var i=0; i<array1.length; i++){
if(array2.includes(array1[i]) === false &&
newArr.includes(array1[i]) === false){
newArr.push(array1[i]);
}
}
}

checkDiff(arr1, arr2);
checkDiff(arr2, arr1);
return newArr;


}