Problem
const getCapitalizedInitials = (name) =>
  name
    .trim()
    .split(" ")
    .forEach((name) => name.charAt(0))
    .join("")
    .toUpperCase()
Solution

We’re treating forEach as if it returned an array, when it actually returns undefined. Instead, we want to use map, which works similar to forEach, but also creates and returns a new array.

const getCapitalizedInitials = (name) =>
  name
    .trim()
    .split(" ")
    .map((name) => name.charAt(0))
    .join("")
    .toUpperCase()