Do you remember, the hypothetical example from Chapter 4, On Navigation, Footers, Alerts, and Content, where MyPhoto only supports browsers above certain versions? We added a Bootstrap alert to our page, which notified visitors that their browser is not supported. Up until now, however, we had no way to actually identify which browser or browser version a MyPhoto visitor was using. Lacking any logic to hide or display the alert, the alert was visible regardless of whether or not the user's browser was actually supported by our website. Now the time has come for us to implement this missing logic.
Web browsers identify themselves by specifying their name and version information using a special field called User-Agent, which is part of the HTTP Request Header (refer to figure 5.1). JavaScript allows users to access this field using the window.navigator property...
