fibonacci-1.js

function fibonacci(n){
    // the base case: when the `n` is 1 or less then the number would be `1`
    if(n <= 1){
        return 1;
    }
    
    //  otherwise we would want to get the previous 
    //  two numbers and add them up.
    return fibonacci(n-1) + fibonacci(n-2);
}