Learning Javascript Cheat Sheet by kelt

// single line comment
//  great place to store your thoughts

/*
    this is a multi-line comment
    everything in here is ignored
*/

if (person.favoriteColor === 'red') {
    // give person a rose
}
else if (person.favoriteColor === 'blue') {
    // give person a violet
}
else {
    // tell person a poem
}

var year = 2016;

while (year < 2020)
{
   console.log("Party like it's ", year);

   // shorthand for: year = year + 1;
   year++;
}


for (var year = 2016; year < 2020; year++)
{
   // no need to increment year in here
   // because it is done in the for loop

   console.log('...', year);
}

// Scopes are controlled by brackets { }
// an outer scope cannot use variables
// declared inside inner scopes
// but an inner scope can use variables
// declared in the outer scope

// outside scope
var x = 1;
var y = 2;
var z = 3;
var result;

function testingScope ( z )
{
   // new variable inside function scope
   var w = 4;

   // y is scoped to this function
   // doesn't affect outer y
   var y = x;  
   
   // z is a function parameter
   // so it's scope is local to function
   z = z + w;  

   // updating x in outer scope
   x = 2;       

  return z;   // returns 8
}

result = testingScope(4);

/*
    w is undefined in outer scope
    x changed to 2
    y is still 2
    z still 3
    result is 8

*/

var answer    = 42;      // number

var duckSays  = 'quack'; // strings ' & "

var isAwesome = true;    // boolean

var emptiness = null;    // null

var catNames  = [        // array of strings
   'princess',
   'fizzy',
   'zoro'
];

var cat       = {        // a single object
   name: catName[2],     // zoro
   age:  10
};

function callMeShirley()
{
   console.log('Surely, we can learn Javascript in 20 minutes?!');
}

function dontCallMeShirley()
{
   console.log('Don't call me Shirely');
}

// runs every 1000 milliseconds (1 second)
var interval = setInterval(callMeShirley, 1000);

// runs once after 5 seconds
var timeout = setTimeout(dontCallMeShirley, 5000);

function addTogether(x, y)
{
   return x + y;
}

var z = addTogether(1, 2);

var addEm = addTogether;

var add = function(x, y)
{
   return x + y;
}

var myObj = {
   add: function(x, y) {
      return x + y;
   }
}

myObj.addEm = addTogether;

// constructor called for "new Person"
function Person(name)
{
  this.name = name;
}

// all person's that are created will have
// this function available
Person.prototype.changeName = function(newName)
{
  this.name = newName;
}

var person = new Person("Bob");

person.changeName('Sponge');

<button id="clickMe">Surely, You'll Click Me</button>

var button = document.getElementById('clickMe');

button.onclick = callMeShirley;

// get mouse position without jQuery

document.onmousemove = handleMouseMove;

function handleMouseMove(event)
{
  var dot, eventDoc, doc, body, pageX, pageY;

  event = event || window.event;

  if (event.pageX == null && event.clientX != null)
  {
      eventDoc = (event.target && event.target.ownerDocument) || document;
      doc = eventDoc.documentElement;
      body = eventDoc.body;

      event.pageX = event.clientX +
         (doc && doc.scrollLeft || body && body.scrollLeft || 0) -
         (doc && doc.clientLeft || body && body.clientLeft || 0);
      event.pageY = event.clientY +
         (doc && doc.scrollTop  || body && body.scrollTop  || 0) -
         (doc && doc.clientTop  || body && body.clientTop  || 0 );
  }
}


// get mouse position with jQuery

$('body').on('mousemove', function(event)
{
   var mousePosition = { x: event.clientX, y: event.clientY };
});