2 Ways to Merge Arrays in JavaScript | SamanthaMing.com
Here are 2 ways to combine your arrays and return a NEW array. I like using the Spread operator. But if you need older browser support, you should use Concat. Alternatively, you can also write the concat method, in this regard: As you can see, this way of writing it doesn't manipulate or change the existing array.
https://www.samanthaming.com/tidbits/49-2-ways-to-merge-arrays/