Objects
are the definable elements of the browsers operating environment. JavaScript uses objects to provide input and manipulate outputs. There are many objects. The window you are viewing this in is an object, and so is the document itself. JavaScript recognizes many objects, but you can also create your own objects. Consider an object you are familiar with, like your watch.We can indetify that object as: watch
Objects have predefined Properties. Some of the properties of this document include its title, specified in the HTML tag <title>, and its background color, specified in the HTML tag <body bgcolor=. You can also assign additional properties to an object. The properties the watch object watch could be: watch.hands or watch.face or watch.digital.timer
Objects can also have Methods, or commands scripted to the object, that specify an action for the object. A method is used to manipulate an object. For example, a method to keep a browser window on top would be self.focus(). The methods used to manipulate your watch could be: watch.tick() or watch.digital.timer.start().
Event Handlers act as triggers causing an object to react to an event. Event handlers invoke an objects methods, or call functions defined in the script. In the example of your watch, an event handler onStart could be used to invoke a watch method onStart="timer.start()".
Objects are grouped in a Hierarchy, objects can be subsets of other objects. The hierarchy is a reference for accessing a documents objects, to determine the properties of those objects, or invoke the methods of those objects. If you think of your watch again you may refer to it in a hierarchy:
| belongings | ||||||
| wardrobe | accessories | |||||
| shoes | suit | ties | watch | |||
therefore, your watch could be called
belongings.accessories.watch
to access the property time
belongings.accessories.watch.time
to use the method start
belongings.accessories.watch.timer.start()