Can't acces the global variable using RECURSION

Hello people I'm new to Javascipt.

Trying to print Fibonacci in Reverse by Recursion. example: RevFib(5) => 3,2,1,1,0

here is the code which works fine.

function fibo(n, a, b)
{   
    
    if (n > 0) {

        
        // Function call
        fibo(n - 1, b, a   b);
        
        // Print the result
       console.log(a);
       
    }
 
}

fibo(5,0,1);

this works fine. but I don't want to output on console. instead I wanted to return a array contain all fibonacci numbers in reverse like [3,2,1,1,0].

I tried to implement it using defining a global array then try to passing that array in fibo() function. It doesn't work. don't know why.

here is the array code:

var arr = [];

function fibo(n, a, b, arr)
{   
    
    if (n > 0) {

        
        // Function call
        fibo(n - 1, b, a   b, arr);
        
        // Print the result
       console.log(a ' - ' arr);
       arr.push(a);
    }
 
}

fibo(5,0,1);

the output is error:

Uncaught TypeError: arr is undefined

as a newbie in JS. I can't get what went wrong. someone tell whats wrong here. Thanks

CodePudding user response：

You're naming a function parameter called arr. Did you mean to do call fibo like so?:

function fibo(n, a, b, arr) {   
    if (n > 0) {
        fibo(n - 1, b, a   b, arr);
        console.log(a   ' - '   arr);
        arr.push(a);
    }
}

let arr = [];

fibo(5, 0, 1, arr);

You also don't need arr to be a global variable if you're going to pass it as a function argument. Generally you should avoid globals (unless you have a special use case), because they make code harder to maintain. Passing the array to the fibo function is the right idea.

You could even have a wrapper function to make usage of return types.

function fiboRecurse(n, a, b, arr) {   
    if (n > 0) {
        fiboRecurse(n - 1, b, a   b, arr);
        console.log(a   ' - '   arr);
        arr.push(a);
    }
}

function fibo(n) {
    let arr = [];
    fiboRecurse(n, 0, 1, arr);
    return arr;
}

console.log(fibo(5));

CodePudding user response：

You are naming a function parameter "arr" as well. The global variable will therefore not be accessible.

CodePudding user response：

You were almost there with your own code. A few tweaks and it runs smoothly:

function fibo(n, a=0, b=1, arr=[]){   
 if (n > 0) {
  fibo(n-1,b,a b, arr);
  arr.push(a);
 }
 return arr
}

const res=fibo(6);

console.log(res)

I used "optional arguments" in the function definition. If they are omitted at calling time they will have the values given in the function definition.