Works in VSCode but not in freecodecamp?

Tell us what’s happening:
I’m getting “ReferenceError: assignment to undeclared variable sum” in the freecodecamp environment but it works in visual studio code.

I’ve found the solution that works for freecodecamp:

“const sum = second =>
typeof second === “number” ? args[0] + second : undefined
return sum”

can anyone explain the discrepancy and which version is more correct?

many thanks!

Your code so far

function addTogether() {
let args = Array.from(arguments)
if (!args.every(elem => typeof(elem) === "number"))
  return undefined

if (args.length > 1)
  return args.reduce((acc, cur) => acc + cur)

return sum = second =>
  typeof second === "number" ? args[0] + second : undefined


Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:76.0) Gecko/20100101 Firefox/76.0.

Challenge: Arguments Optional

Link to the challenge:

freeCodeCamp challenges run in Strict Mode. If you are working on code outside of the freeCodeCamp editor, you should also enable Strict Mode.

You can just return an anonymous function instead.

return second =>
    typeof second === "number" ? args[0] + second : undefined;