Use Feature Detection Over Browser User Agent

The userAgent string is a poor indicator of whether a particular feature (or bug) is present. To compound the problem, much of the code that interprets userAgent does so incorrectly. For example, one browser-sniffing library expected the major version to be only a single digit, so it reported Firefox 15 as Firefox 1 and IE 10 as IE 1! It is more reliable to detect the feature or problem directly, and use that as the decision criteria for code branches. We recommend Modernizr as the easiest way to implement feature detection.