functions.js

alert = console.log

function map(f, a) {
  var result = []; // Create a new Array
  var i; // Declare variable
  for (i = 0; i != a.length; i++)
    result[i] = f(a[i]);
  return result;
}

var f = function(x) {
   return x * x * x; 
}

var numbers = [0, 1, 2, 5, 10];
var cube = map(f,numbers);
console.log(cube);

////////////////////////////////////////

function outside(x) {
  function inside(y) {
    return x + y;
  }
  return inside;
}

fn_inside = outside(3); // Think of it like: give me a function that adds 3 to whatever you give
                        // it
console.log(result = fn_inside(5)); // returns 8

console.log(result1 = outside(3)(5)); // returns 8

////////////////////////

function A(x) {
  function B(y) {
    function C(z) {
      console.log(x + y + z);
    }
    C(3);
  }
  B(2);
}
A(1); // logs 6 (1 + 2 + 3)

////////////////////////////

var pet = function(name) {   // The outer function defines a variable called "name"
  var getName = function() {
    return name;             // The inner function has access to the "name" variable of the outer 
                             //function
  }
  return getName;            // Return the inner function, thereby exposing it to outer scopes
}
myPet = pet('Vivie');
   
console.log(myPet());

///////////////////////////////

var getCode = (function() {
  var apiCode = '0]Eal(eh&2';    // A code we do not want outsiders to be able to modify...
  
  return function() {
    return apiCode;
  };
})();

console.log(getCode());    // Returns the apiCode

////////////////////////////////

var a = [
  'Hydrogen',
  'Helium',
  'Lithium',
  'Beryllium'
];

var a2 = a.map(function(s) { return s.length; });

console.log(a2); // logs [8, 6, 7, 9]

var a3 = a.map(s => s.length);

console.log(a3); // logs [8, 6, 7, 9]

{
  function sumAll(...args) { // args is the name for the array
    let sum = 0;

    for (let arg of args) sum += arg;

    return sum;
  }

  alert( sumAll(1) ); // 1
  alert( sumAll(1, 2) ); // 3
  alert( sumAll(1, 2, 3) ); // 6
}


{
  function showName(firstName, lastName, ...titles) {
    alert( firstName + ' ' + lastName ); // Julius Caesar

    // the rest go into titles array
    // i.e. titles = ["Consul", "Imperator"]
    alert( titles[0] ); // Consul
    alert( titles[1] ); // Imperator
    alert( titles.length ); // 2
  }

  showName("Julius", "Caesar", "Consul", "Imperator");
}

{
  function showName() {
    alert( arguments.length );
    alert( arguments[0] );
    alert( arguments[1] );

    // it's iterable
    // for(let arg of arguments) alert(arg);
  }

  // shows: 2, Julius, Caesar
  showName("Julius", "Caesar");

  // shows: 1, Ilya, undefined (no second argument)
  showName("Ilya");
}

{
  let sum = new Function('a', 'b', 'return a + b');

  alert( sum(1, 2) ); // 3
}

{
  let sayHi = new Function('alert("Hello")');

  sayHi(); // Hello
}

{
  function getFunc() {
    let value = "test";

    let func = new Function('alert(value)');

    return func;
  }

  // getFunc()(); // error: value is not defined
}

{
  function getFunc() {
    let value = "test";

    let func = function() { alert(value); };

    return func;
  }

  getFunc()(); // "test", from the Lexical Environment of getFunc
}