callback&functional programming.js

const _ = require('lodash');

const log = {
  describe(str) {
    console.log(`describe: ${str}`);
  },

  it(str) {
    console.log(`\t it ${str}`);
  },

  assertEquals(str) {
    console.log(`\t\tResult: ${str}`);
  },

  error(str) {
    console.log(`\t\tResult: ${str}`);
  },
};

test();

function test() {
  describe('add', function() {
    it('should return a empty object when input is undefined', function() {
      function afterAdded(sum) {
        console.log('Sum:', sum);
      }

      const actual = add(1, 2, afterAdded);
    });
  });
}
const x = {
  val: 2,
};

const f = x => Object.assign({}, x, { val: x.val + 1 });

const g = x => Object.assign({}, x, { val: x.val * 2 });

console.log(f(g(x)));

function add(a, b) {
  console.log(new Date());
  return a + b;
}

function describe(description, fn) {
  log.describe(description);

  fn();
}

function it(sentence, fn) {
  log.it(sentence);

  fn();
}

// curry function
function addNew(a) {
  return function(b) {
    return a + b;
  };
}

// curry function
function multiple(a) {
  return function(b) {
    return a * b;
  };
}

const inc = addNew(1);
const double = multiple(2);

console.log(inc(1));
console.log(double(3));

const logF = console.log.bind();

// setTimeout(function() {
//   console.log('Hi');
// }, 3000);

// function hoisting
// event loop
// apply(), call(), bind()

function generateTimeout(second) {
  // Closure
  return function(fn) {
    setTimeout(fn, second * 1000);
  };
}

// const timeout3s = generateTimeout(3);

/*

timeout3s = function(fn) {
  setTimeout(function() {
    logF('Hi');
  }, 3 * 1000);
}

*/

// timeout3s(function() {
//   logF('Hi');
// });

const menuItems = [
  { name: 'Home', path: '/home' },
  { name: 'Dashboard', path: '/dashboard' },
];

// url=> https://localhost:3000/dashboard?xxx=1

function subIsActive(menuItem) {
  const menuItems = Array.isArray(menuItem) ? menuItem : [menuItem];
  return menuItems.some(menuItem => {
    return '/dashboard?xxx=1'.indexOf(menuItem.path) === 0;
    // current path starts with this path string
  });
}

console.log(subIsActive(menuItems[1]));

function assertEquals(expected, actual) {
  if (_.isEqual(expected, actual)) {
    log.assertEquals('Passed');
  } else {
    log.error(`${JSON.stringify(actual)} is not expected as ${JSON.stringify(expected)}`);
  }
}

function assertError(fn, message = '') {
  try {
    fn();

    log.error('Expected an error');
  } catch (error) {
    log.assertEquals('Passed');
  }
}