diff --git a/arrayUtils/arrayUtils.js b/arrayUtils/arrayUtils.js
index 1ab7a87..dcca903 100644
--- a/arrayUtils/arrayUtils.js
+++ b/arrayUtils/arrayUtils.js
@@ -2,12 +2,12 @@ import { randomNumberBetween } from "../other.js"
 
 export function first(array, n = 1) {
   if (n === 1) return array[0]
-  return array.filter((_, index) => index < n)
+  return array.slice(0, n)
 }
 
 export function last(array, n = 1) {
   if (n === 1) return array[array.length - 1]
-  return array.filter((_, index) => array.length - index <= n)
+  return array.slice(-n)
 }
 
 export function sample(array) {
@@ -16,6 +16,7 @@ export function sample(array) {
 
 export function pluck(array, key) {
   return array.map(element => element[key])
+              .filter(element => element !== undefined)
 }
 
 export function groupBy(array, key) {