How can i reduce the time of execution of this code

Question

var yourself = {
    fibonacci : function(n) {
        return n === 0 ? 0 : n === 1 ? 1 : 
        this.fibonacci(n -1) + this.fibonacci (n-2)
    }
};

This function is constantly setting the value of its 'fibonacci' property based on the arguement supplied for 'n' parameter of the function. I would like to refactor the function to reduce execution time

Answer 1

You could implement some kind of caching. This way you don't need to recalculate the same result multiple times.

var yourself = {
    fibonacci : function(n, cache = new Map()) {
        if(cache.has(n)) return cache.get(n);
        if(n === 0) return 0;
        if(n === 1) return 1;
        
        const start = this.fibonacci(n-1, cache);
        const end = this.fibonacci(n-2, cache);
        
        cache.set(n-1, start);
        cache.set(n-2, end);
        
        return start + end;
    }
};

console.log(yourself.fibonacci(40));