var a = function a(){
  this.x = 1;
  return this;
}
var l = {
  x:1
};
a.prototype.inc = function(){ return this.x+1; }
l.inc = function(){ return this.x+1; }

var b = new a();
var c = a();

console.log('b =',typeof b, b);
console.log('c =',typeof c, c);
console.log('l =',typeof l, l);
console.log('b.x =', b.x);
console.log('b.inc() = ',b.inc());
console.log('l.x =', l.x);
console.log('l.inc() = ',l.inc());
console.log('c.x = ', c.x);
console.log('c.inc() = ',c.inc());

/*

b = object a {x: 1, inc: function}
c = object Window {...}
l = object Object {x: 1, inc: function}

b.x = 1
b.inc() =  2

l.x = 1
l.inc() =  2

c.x =  1
Uncaught TypeError: undefined is not a function

*/