Recursive Problems and Solutions in JavaScript

Recursive Problems and Solutions

Factorial

function factorial(n) {
  if (n <= 1) return 1;
  return n * factorial(n - 1);
}

Fibonacci

function fib(n) {
  if (n < 2) return n;
  return fib(n - 1) + fib(n - 2);
}

Flatten Nested Arrays

function flatten(arr) {
  return arr.reduce((acc, item) =>
    acc.concat(Array.isArray(item) ? flatten(item) : item), []);
}

Tree Traversal (DFS)

function traverse(node, callback) {
  callback(node);
  if (node.children) node.children.forEach(child => traverse(child, callback));
}

Power

function power(base, exp) {
  if (exp === 0) return 1;
  return base * power(base, exp - 1);
}

Reverse String

function reverse(str) {
  if (str.length <= 1) return str;
  return reverse(str.slice(1)) + str[0];
}

The Takeaway

Common recursive problems: factorial (n * factorial(n-1)), fibonacci (fib(n-1) + fib(n-2)), flatten (reduce + concat), tree traversal (forEach + recurse), power (base * power(base, exp-1)), and reverse string (recurse on slice + first char).