Javascript using Globals.

Using Javascript Globals.

• Javascript has a predefined global object, which serves as a placeholder for the global properties and global functions.
• All the Javascript build-in objects such as Object, Number, String and Date are considered as global properties.
• Functions and variables that you define outside of a function or object of any kind is to be regarded as a global property.
  
  

  function print(str){     // 'print' is a global function
      document.write(str+"<br>");
    }
    var mystr="Hello"; // 'mystr' is a global string

• The global object has no name, but if your host environment is the web browser, the global object is called window.
• You can also on the top-level of Javascript use the this keyword as a reference to the global object.
• You cannot create new global object, as there is no Global constructor function.
• All pre-defined properties in the global object is non-enumerable in the core of Java Script. All of the other global properties (global variables) allows you to list with a for / in loop like this:
  
  

  <script type="text/javascript">
  var variables = ""
  for(var propname in this){
      variables += propname+" is typeof "+typeof this[propname] + "<br>";
  }
  document.write(variables+"<br>");
  </script>