Recursive fibonacci sequence

fib.js

/**
 * Generate the fibonaccie sequence recursively
 * @param {number} num amount of recursion
 * @returns {array} fibonacci sequence
 */
let fib = num => {
    if (num == 1) return [1];
    else {
        let prev = fib(num - 1);
        return prev.concat((prev[prev.length - 2] || 0) + prev[prev.length - 1])
    }
}