For your base case, think about what number you want to return. If I called your function as sum([1,2,3], 0) that means that I want to return the sum of the first 0 elements in the array, or otherwise, the sum of none of the elements. If you aren’t summing up any elements, what do you think a good return value would be?

Remember, this is the sum of the elements. Should you really be multiplying them when you hit the else and make the recursive call?

There is one more issue after the two above. Think about what the value of n is when you are accessing a value from the array.

I’m going to take a wild guess here and assume you know how to add two numbers together in JS? Remember, the function sum always returns a number. So you can add a number to whatever the recursive call to sum returns.

There is not much difference here between the multiply function in the example and the sum function you are trying to implement.

What part of that don’t you understand? Did you study the instructions and example? As I mentioned, the example is basically the same thing as what you are asked to do with sum.

Please do not just keep repeating that you don’t understand. We need to know exactly what you don’t understand so we know how to help you. I fear I will grow tired of trying to help you if you don’t give me something more to go on.