This sample show how the 'this' keyword refer to a different objects, and thoose scopes are both, global or object related depends on where are you in the current moment.

jsbin.thisKeyword.js

console.clear();

function Blog(){
  
  //bad pratice avoid this
  //if (!(this instanceof blog))
  //  return new blog();
  
  function internal(){
    console.log('internal:' + this);
  }

  this.external = function(){
    console.log('external:' + this);
    internal();
  }
  this.external();
  
}



console.log('called with global scope');
Blog();

console.log('called with Blog Object Scope');
var blogObj = new Blog(); 
blogObj.external();