In Hour 9, “Working with the Document Object Model,” you learned about the various objects (such as window and document) that represent portions of the browser window and the current Web document. JavaScript also includes an object called navigator that you can use to read information about the user's browser.
The navigator object isn't part of the DOM, so you can refer to it directly. It includes a number of properties, each of which tells you something about the browser. These include the following: