recursive practice

recursive.js

// helper functions
const format = data => JSON.stringify(data);

const title = title => console.log(`\n${title}\n---------------------`);

const iterate = (fnName, fn) => {
  [1, 2, 3, 4, 5].forEach(n => {
    console.log(`${fnName}(${n}) = ${fn(n)}`);
  });
};

// WRITE FUNCTIONS IN A RECURSIVE WAY
// pow, fibonaci, factorial, map, reverse, sumSalaries

const pow = (b, n) => (n === 1 ? b : b * pow(b, n - 1));

const fibonaci = x => (x <= 1 ? 1 : fibonaci(x - 1) + fibonaci(x - 2));

const factorial = x => (x === 1 ? 1 : x * factorial(x - 1));

const map = (arr, fn) => (arr.length === 0 ? [] : fn(arr[0]).concat(map(arr.slice(1), fn)));

const reverse = s => (s.length === 1 ? s : s.slice(-1) + reverse(s.slice(0, -1)));

const sumSalaries = department => {
  const isDepartment = Array.isArray(department);
  if (isDepartment) {
    return department.reduce((acc, person) => acc + person.salary, 0);
  } else {
    let sum = 0;
    for (dept in department) {
      sum += sumSalaries(department[dept]);
    }
    return sum;
  }
};

// ==========================================================

// pow
title("pow");
const powOfBase2 = n => pow(2, n);
iterate("powOfBase2", powOfBase2);

// fibonaci
title("fibonaci");
iterate("fibonaci", fibonaci);

// factorial
title("factorial");
iterate("factorial", factorial);

// map
title("map");
const lettersArray = "abcde".split("");
const uppercase = x => x.toUpperCase();
console.log(`map(${format(lettersArray)}, uppercase) = ${map(lettersArray, uppercase)}`);

// reverse
title("reverse");
const word = "abcde";
console.log(`reverse(${format(word)}) = ${reverse(word)}`);

//sumSalaries
title("sumSalaries");
const company = {
  sales: [{ name: "John", salary: 1000 }, { name: "Alice", salary: 600 }],
  development: {
    sites: [{ name: "Peter", salary: 2000 }, { name: "Alex", salary: 1800 }],
    internals: [{ name: "Jack", salary: 1300 }]
  }
};
console.log(`sumSalaries(company) = ${sumSalaries(company)}`);