const ops = {
  add: (a, b) => a + b,
  subtract: (a, b) => a - b,
  multiply: (a, b) => a * b,
  divide: (a, b) => b !== 0 ? a / b : NaN,
};

const pipeline = (...fns) => (value) => fns.reduce((acc, fn) => fn(acc), value);

const double  = (x) => ops.multiply(x, 2);
const addTen  = (x) => ops.add(x, 10);
const halve   = (x) => ops.divide(x, 2);
const subtractThree = (x) => ops.subtract(x, 3);

const transform = pipeline(double, addTen, halve, subtractThree);

const results = [5, 0, -4].map(transform);
console.log(results);

const values = [0.1 + 0.2, NaN, Infinity, -0, 42.6789];

const results = values.map((v, i) => {
  if (i === 0) return Number.isInteger(v) + " | " + v.toFixed(2);
  if (i === 1) return Number.isFinite(v) + " | " + Number.isNaN(v);
  if (i === 2) return Number.isFinite(v) + " | " + Number.MAX_SAFE_INTEGER;
  if (i === 3) return Object.is(v, -0) + " | " + (v === 0);
  if (i === 4) return v.toFixed(2) + " | " + v.toPrecision(4);
});

results.forEach(r => console.log(r));

const items = [
  { name: "banana", price: 1.5, qty: 10 },
  { name: "apple",  price: 1.5, qty: 5  },
  { name: "cherry", price: 3.0, qty: 8  },
  { name: "date",   price: 2.0, qty: 8  },
];

const sorted = [...items].sort((a, b) => {
  if (a.price !== b.price) return a.price - b.price;
  if (a.qty   !== b.qty)   return b.qty   - a.qty;
  return a.name.localeCompare(b.name);
});

console.log(sorted.map(i => `${i.name}:${i.qty}`).join(", "));

class DatabaseError extends Error {
  constructor(message, code) {
    super(message);
    this.name = "DatabaseError";
    this.code = code;
  }
}

class ConnectionError extends DatabaseError {
  constructor(host) {
    super(`Failed to connect to ${host}`, 503);
    this.name = "ConnectionError";
    this.host = host;
  }
}

const err = new ConnectionError("db.server.io");

console.log([
  err instanceof ConnectionError,
  err instanceof DatabaseError,
  err instanceof Error,
  err.name,
  err.code,
  err.message,
].join(" | "));

const compose = (...fns) => (x) => fns.reduceRight((acc, fn) => fn(acc), x);
const pipe = (...fns) => (x) => fns.reduce((acc, fn) => fn(acc), x);

const double = (x) => x * 2;
const addTen = (x) => x + 10;
const square = (x) => x ** 2;
const negate = (x) => -x;

const transform1 = compose(negate, square, addTen, double);
const transform2 = pipe(double, addTen, square, negate);

const memoize = (fn) => {
  const cache = new Map();
  return (x) => {
    if (!cache.has(x)) cache.set(x, fn(x));
    return cache.get(x);
  };
};

const memoTransform1 = memoize(transform1);

console.log(transform1(3));
console.log(transform2(3));
console.log(memoTransform1(3) === transform1(3));

function processData(value) {
  let result = "start";

  try {
    result += " -> try";
    if (value === null) throw new TypeError("Null value");
    if (value < 0) throw new RangeError("Negative value");
    result += " -> success";
    return result;
  } catch (e) {
    result += ` -> catch(${e.constructor.name})`;
    return result;
  } finally {
    result += " -> finally";
    console.log(result);
  }
}

console.log(processData(null));

function createCounter() {
  let count = 0;

  return {
    increment() { count++; },
    decrement() { count--; },
    getCount() { return count; },
    reset: () => { count = 0; }
  };
}

const counter = createCounter();
counter.increment();
counter.increment();
counter.increment();
counter.decrement();

const { getCount, reset } = counter;

console.log(counter.getCount());
reset();
console.log(getCount());