feat: replace flattenArray with build-in Array.flat function

src/animatables.js

@@ -8,7 +8,6 @@ import {
 
 import {
   is,
-  flattenArray,
   filterArray,
   arrayContains,
   toArray,
@@ -32,7 +31,7 @@ function registerTarget(target) {
 }
 
 function parseTargets(targets) {
-  const targetsArray = targets ? (flattenArray(is.arr(targets) ? targets.map(toArray) : toArray(targets))) : [];
+  const targetsArray = targets ? (is.arr(targets) ? targets.map(toArray).flat() : toArray(targets).flat()) : [];
   return filterArray(targetsArray, (item, pos, self) => self.indexOf(item) === pos);
 }
 

src/keyframes.js

@@ -1,7 +1,6 @@
 import {
   is,
   mergeObjects,
-  flattenArray,
   filterArray,
 } from './utils.js';
 
@@ -52,7 +51,7 @@ function convertPropertyValueToTweens(propertyName, propertyValue, tweenSettings
 
 function flattenParamsKeyframes(keyframes) {
   const properties = {};
-  const propertyNames = filterArray(flattenArray(keyframes.map(key => Object.keys(key))), p => is.key(p))
+  const propertyNames = filterArray(keyframes.map((key) => Object.keys(key)).flat(), p => is.key(p))
   .reduce((a,b) => {
     if (a.indexOf(b) < 0) {
       a.push(b);

src/utils.js

@@ -67,10 +67,6 @@ export function filterArray(arr, callback) {
   return result;
 }
 
-export function flattenArray(arr) {
-  return arr.reduce((a, b) => a.concat(is.arr(b) ? flattenArray(b) : b), []);
-}
-
 export function toArray(o) {
   if (is.arr(o)) return o;
   if (is.str(o)) o = selectString(o) || o;