This snippet computing the golden ratio field.

scale.js

function scale(n){
    if(n === 0) return 1;
    if(n === 1) return 1.618;
    if(n === -1) return 0.618;

    if(n > 0){
        return scale(n-1) + scale(n-2);
    }
    if(n < 0){
        return scale(n+2) - scale(n+1);
    }
}
console.log(scale(0));  // 1 
console.log(scale(1));  // 1.618
console.log(scale(4));  // 6.854

console.log(scale(-1)); // 0.618
console.log(scale(-2)); // 0.382