closuresandscope.js

// we're starting this function with an IIFE http://benalman.com/news/2010/11/immediately-invoked-function-expression/
// it's important to start this with a semicolon because otherwise any previously loaded JavaScript might try and invoke
// its last line using the anonymous function that we define here as its argument, and then invoke the resulting return value
// on line 63. That would be silly, yo. So we explicitly end the previous thought with a semicolon.

;(function () {
  
  // CLOSURES
  function captureWhatNumberIsRightNow (number) {
    return function () {
      return number;
    }
  }

  var number = 6
  itWasSix = captureWhatNumberIsRightNow(number);
  number = 5
  itWasFive = captureWhatNumberIsRightNow(number);
  itWasTwelve = captureWhatNumberIsRightNow(12);

  window.number = 142

  console.log(itWasSix())
  console.log(itWasFive())
  console.log(itWasTwelve())


  // THIS

  function introduceYoSelf () {
    console.log('my name is ' + this.name);
  }

  function Person (name) {
    this.name = name;
  }

  Person.prototype.sayHi = introduceYoSelf

  johnLennon = new Person('John')
  johnLennon.sayHi()

  ringoStarr = new Person('Ringo')
  ringoStarr.sayHi()

  introduceYoSelf()

  function whatIsThis () {
    console.log(this);
  }

  whatIsThis.call(ringoStarr)
  whatIsJohn = whatIsThis.bind(johnLennon)
  whatIsThis()

  Person.prototype.addAButtonToTheScreen = function () {
    var button = document.createElement('button')
    document.body.appendChild(button)
    button.innerText = this.name
    button.addEventListener('click', this.sayHi.bind({name: 'Sherif is super awesome'}));
  }

})()