Reduce method of array not reaching last element

Question

So I'm really new to JavaScript, and I'm having a bit trouble with reduce method in JavaScript which doesn't reach the last element of the array. My function removes duplicates from array by first sorting the array, and then using the reduce method to delete element if first and second element are same.

I'm thinking maybe it has something to do with the splice method I use in conjunction with it. But I'm not entirely sure what is going on, can someone help explain what's happening here?

function removeduplicate3(arr) {
  arr.sort((first, second) => (first > second));
  console.log(arr);
  arr.reduce((first, second) => {
    console.log(`${first} ${second}`); // check pair of elements it reduces
    if (first === second) {
      arr.splice(arr.indexOf(second), 1)
      return first;
    } else
      return second;
  }, undefined);
}

let arr = ["Hello", "World", "Bye", "World", "I", "Am", "I", "World"];

console.log(removeduplicate3(arr));

my finally (incorrectly) filtered array has: [ "Am", "Bye", "Hello", "I", "World", "World" ]

I printed the pairs of elements of array with ${first} ${second}, and it's missing the last pair: World World

This doesn't make sense. The callback function doesn't receive pairs of elements. — Barmar, Feb 08 '22 at 02:57
You're not sorting the array correctly. Use `arr.sort((first, second) => first.localeCompare(second));` — Barmar, Feb 08 '22 at 03:03
Check the results of your sort, it isn't what you think it is. Just use `arr.sort()` — Jon P, Feb 08 '22 at 03:03
And the function doesn't return anything, you need to return the result of `arr.reduce()`. — Barmar, Feb 08 '22 at 03:04
And the callback function has to return the array that you want as the result. — Barmar, Feb 08 '22 at 03:05
oh my god, I see it as Array(8) [ "Am", "Bye", "Hello", "I", "I", "World", "World", "World" ], and when I press the down key, it gives me only 6 elements. I'm never using console.log(arr) again. — Asphodel, Feb 08 '22 at 03:06
See [this answer](https://stackoverflow.com/a/15868720/1491895) for how to use `reduce` to remove duplicates. — Barmar, Feb 08 '22 at 03:06
_"I'm never using console.log(arr) again"_... I wish others would follow this lead — Phil, Feb 08 '22 at 03:10

Reduce method of array not reaching last element

0 Answers0