user agent matching on the client-side

user-agent-match.js

/** User-agent pattern matching */
var browser = 'unknown'
  , version = 'unknown'
  , patterns = {
        android:    /android\s([0-9.]*)/i
        chrome:     /chrome\/([0-9.]*)/i,
        firefox:    /firefox\/([0-9.]*)/i,
        ie:         /msie\s([0-9.]*)/i,
        ipad:       /ipad.version\/([0-9.]*).safari/i,
        iphone_4:   /iphone\sos\s4.version.mobile\/([0-9.]*).safari/i,
        iphone_5:   /iphone\sos\s5.version.mobile\/([0-9.]*).safari/i,
        safari:     /version\/([0-9.]*).safari/i
    }
  , key, matches;

for (key in patterns) {

    matches = navigator.userAgent.match(patterns[key]);

    if (matches) {
        browser = key;
        version = matches[1];
        break;
    }
}

console.log(browser, version);