* Most of the material is taken from here.

• Variables
  JavaScript has dynamic types.
  var x = 5.
  JavaScript has only one type of numbers.
  By re-declaring a variable, it does not lose its value.
  
• types
  There are 6 types: 4 primitive types (string, number, boolean, undefined), 2 complex types (function, object).
  A primitive data doesn't have any properties or methods.
  null and undefined both have value undefined, but null is of type object and undefined is of type undefined.
  Arrays and dictionaries (called 'objects' in JS) are of type object.
• Functions
  

  function myFunction(arg1, arg2) {
      ... ;
      return ...;
  }
  

  
  
• Misc.
  When adding a number and a string, JavaScript will treat the number as a string.
  ===  equal value and equal type
  ?  ternary operator