Array Reduce for the Uninitiated

Hello!

The title is a pun. Let me explain:

let randoArr = [1, 2, 3, 4, 5, 6, 7, 8, 10]

let someNum = array.reduce((acc, num) => {

   if(num % 2 === 0){

      return acc.concat(num);   

   } 

}, [])

This code snippet above won't work. Apparently upon the first go around, the initiated value gets wiped. Who knew? I didn't...