nhb-toolbox/dist/esm/number/fibonacci.js

A versatile collection of smart, efficient, and reusable utility functions and classes for everyday development needs.

/**
 * * Generates the first `limit` Fibonacci numbers.
 *
 * @param limit The number of Fibonacci numbers to generate.
 * @returns An array containing the first `limit` Fibonacci numbers.
 */
export function getFibonacciSeries(limit) {
    const cLimit = Number(limit);
    if (!Number.isFinite(cLimit) || cLimit <= 0) {
        return [];
    }
    if (cLimit === 1)
        return [0];
    const series = [0, 1];
    for (let i = 2; i < cLimit; i++) {
        series.push(series[i - 1] + series[i - 2]);
    }
    return series;
}
/**
 * * Generates the first `limit` Fibonacci numbers using recursion with memoization.
 *
 * @param limit - The number of Fibonacci numbers to generate.
 * @returns An array containing the first `limit` Fibonacci numbers.
 */
export function getFibonacciSeriesMemo(limit) {
    const cLimit = Number(limit);
    if (!Number.isFinite(cLimit) || cLimit <= 0)
        return [];
    if (cLimit === 1)
        return [0];
    const memo = new Map([
        [0, 0],
        [1, 1],
    ]);
    const fib = (n) => {
        if (memo.has(n))
            return memo.get(n);
        const val = fib(n - 1) + fib(n - 2);
        memo.set(n, val);
        return val;
    };
    return Array.from({ length: cLimit }, (_, i) => fib(i));
}
/**
 * * Generator function for Fibonacci sequence up to a given limit.
 *
 * @param limit - Number of Fibonacci numbers to generate.
 * @param onYield - Optional callback triggered on each yield with the current value and index.
 * @returns A generator yielding Fibonacci numbers one by one.
 */
export function* fibonacciGenerator(limit, onYield) {
    const cLimit = Number(limit);
    if (!Number.isFinite(cLimit) || cLimit < 0)
        return;
    let a = 0;
    let b = 1;
    for (let i = 0; i < cLimit; i++) {
        onYield?.(a, i);
        yield a;
        [a, b] = [b, a + b];
    }
}
/**
 * * Calculates the `n`th Fibonacci number using optimized space.
 *
 * @param index - The index (0-based) of the Fibonacci number.
 * @returns The index=`n`th Fibonacci number.
 */
export function getNthFibonacci(index) {
    const n = Number(index);
    if (!Number.isFinite(n) || n < 0)
        return NaN;
    if (n === 0)
        return 0;
    if (n === 1)
        return 1;
    let a = 0, b = 1;
    for (let i = 2; i <= n; i++) {
        [a, b] = [b, a + b];
    }
    return b;
}