JavaScript has a method to flatten nested arrays
Pretty basic, but I just found out js has an awesome .flat() method. Example:
const arr = [ 1, [ 2, 3 ], 4, [ ] ]
console.log(arr) // Output: [ 1, [ 2, 3 ], 4, [] ]
console.log(arr.flat()) // Output: [ 1, 2, 3, 4 ]