fibonacci series using recursion in javascript

How does the fibonacci recursive function "work"?

stackoverflow.com › questions › 8845154 › how-does-the-fibonacci-recursive-function-work

You're defining a function in terms of itself. In general, fibonnaci(n) = fibonnaci(n - 2) + fibonnaci(n - 1). We're just representing this relationship in code. So, for fibonnaci(7) we can observe:

fibonacci(7) is equal to fibonacci(6) + fibonacci(5)
fibonacci(6) is equal to fibonacci(5) + fibonacci(4)
fibonacci(5) is equal to fibonacci(4) + fibonacci(3)
fibonacci(4) is equal to fibonacci(3) + fibonacci(2)
fibonacci(3) is equal to fibonacci(2) + fibonacci(1)
fibonacci(2) is equal to fibonacci(1) + fibonacci(0)
fibonacci(1) is equal to 1
fibonacci(0) is equal to 1

We now have all the parts needed to evaluate fibonacci(7), which was our original goal. Notice that the base case -- return 1 when n < 2 -- is what makes this possible. This is what stops the recursion, so that we can can start the process of unrolling the stack and summing the values we're returning at each step. Without this step, we'd continue calling fibonacci on smaller and smaller values right up until the program finally crashed.

It might help to add some logging statements that illustrate this:

function fibonacci(n, c) {
    var indent = "";
    for (var i = 0; i < c; i++) {
        indent += " ";
    }
    console.log(indent + "fibonacci(" + n + ")");
    if (n < 2) {
        return 1;
    } else {
        return fibonacci(n - 2, c + 4) + fibonacci(n - 1, c + 4);
    }
}

console.log(fibonacci(7, 0));

Output:

fibonacci(7)
    fibonacci(5)
        fibonacci(3)
            fibonacci(1)
            fibonacci(2)
                fibonacci(0)
                fibonacci(1)
        fibonacci(4)
            fibonacci(2)
                fibonacci(0)
                fibonacci(1)
            fibonacci(3)
                fibonacci(1)
                fibonacci(2)
                    fibonacci(0)
                    fibonacci(1)
    fibonacci(6)
        fibonacci(4)
            fibonacci(2)
                fibonacci(0)
                fibonacci(1)
            fibonacci(3)
                fibonacci(1)
                fibonacci(2)
                    fibonacci(0)
                    fibonacci(1)
        fibonacci(5)
            fibonacci(3)
                fibonacci(1)
                fibonacci(2)
                    fibonacci(0)
                    fibonacci(1)
            fibonacci(4)
                fibonacci(2)
                    fibonacci(0)
                    fibonacci(1)
                fibonacci(3)
                    fibonacci(1)
                    fibonacci(2)
                        fibonacci(0)
                        fibonacci(1)

Values at the same level of indentation are summed to produce the result for the previous level of indentation.

Answer from Wayne on Stack Overflow

Programiz

programiz.com › javascript › examples › fibonacci-recursion

JavaScript Program to Display Fibonacci Sequence Using Recursion

// program to display fibonacci sequence using recursion function fibonacci(num) { if(num < 2) { return num; } else { return fibonacci(num-1) + fibonacci(num - 2); } } // take nth term input from the user const nTerms = prompt('Enter the number of terms: '); if(nTerms <=0) { console.log('Enter ...

GeeksforGeeks

geeksforgeeks.org › javascript › javascript-program-to-display-fibonacci-sequence-using-recursion

JavaScript Program to Display Fibonacci Sequence Using Recursion - GeeksforGeeks

July 29, 2024 - The base case for the recursion is when n is less than or equal to 1. In this case, we simply return n itself, as the Fibonacci sequence starts with 0 and 1. For any other value ofn, we recursively call the fibonacci function with n - 1 and ...

Discussions

Recursion with fibonacci

Tell us what’s happening: Describe your issue in detail here. ok so, im like 95% certain my code works but it times out the test. am i making a mistake or is it too memory heavy? **Your code so far** function sumF… More on forum.freecodecamp.org

forum.freecodecamp.org

June 2, 2021

recursion - How does the fibonacci recursive function "work"? - Stack Overflow

I'm new to Javascript and was reading up on it, when I came to a chapter that described function recursion. It used an example function to find the nth number of the Fibonacci sequence. The code ... More on stackoverflow.com

stackoverflow.com

fibonacci using recursion

Don’t use input unless the prompt says to - homework graders have to handle it in a special way, and if they’re not expecting to, your program just blocks on input. More on reddit.com

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January 14, 2023

Can you explain the logic behind a recursive fibonacci function?

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