Diff Two Arrays - why doesn't this work?

JavaScript
1 
function diffArray(arr1, arr2) {
  var newArr = [];
  var arr3 = arr1.concat(arr2).sort();
  
 
  for (i = arr3[0]; i < arr3.length + 1; i++) {
    if (arr3[i] !== arr3[i+1] && arr3[i] !== arr3[i-1])
      newArr.push(arr3[i]);
  }
  return newArr;
}

diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]);
2

What is the problem asking for? When I ran your code I got [4] which is the only difference between the arrays.

3

I’ve edited your post for readability. When you enter a code block into the forum, precede it with a line of three backticks and follow it with a line of three backticks to make easier to read. See this post to find the backtick on your keyboard. The “preformatted text” tool in the editor (</>) will also add backticks around text.

markdown_Forums

4

sorry…this is the intermediate algorithm. This is the problem…Compare two arrays and return a new array with any items only found in one of the two given arrays, but not both. In other words, return the symmetric difference of the two arrays.

5

It worked for those two specific arrays but not for some of the other arrays in problem ie. [“diorite”, “andesite”, “grass”, “dirt”, “pink wool”, “dead shrub”], [“diorite”, “andesite”, “grass”, “dirt”, “dead shrub”]

This one did not work.

6

There’s something very wrong about this line: for (i = arr3[0]; i < arr3.length + 1; i++)

You’ve set i to be the first element of the array, and then incremented it, which I definitely don’t think you meant to do. I think it’s just a happy little accident that it worked for some cases.

Also i < arr3.length + 1 seems very wrong to me, what is arr3[arr3.length]?

I suspect you intended to do for(i=1; i < arr3.length - 1; i++) (based on usingi+1 and i-1)

7

gebulmer…Thank you for the help.

The solution that works includes this:
for (i=0; i<arr3.length; i++)