Mobile UA detection library.You can access device object which contains useful information about device and platform.

ua.js

var device = (function () {
    var device = {};
    var ua = navigator.userAgent;

    var android = ua.match(/(Android);?[\s\/]+([\d.]+)?/);
    var ipad = ua.match(/(iPad).*OS\s([\d_]+)/);
    var ipod = ua.match(/(iPod)(.*OS\s([\d_]+))?/);
    var iphone = !ipad && ua.match(/(iPhone\sOS)\s([\d_]+)/);

    device.ios = device.android = device.iphone = device.ipad = false;
    
    // Android
    if (android) {
        device.os = 'android';
        device.osVersion = android[2];
        device.android = true;
    }
    if (ipad || iphone || ipod) {
        device.os = 'ios';
        device.ios = true;
    }
    // iOS
    if (iphone && !ipod) {
        device.osVersion = iphone[2].replace(/_/g, '.');
        device.iphone = true;
    }
    if (ipad) {
        device.osVersion = ipad[2].replace(/_/g, '.');
        device.ipad = true;
    }
    if (ipod) {
        device.osVersion = ipod[3] ? ipod[3].replace(/_/g, '.') : null;
        device.iphone = true;
    }

    // Webview
    device.webView = (iphone || ipad || ipod) && ua.match(/.*AppleWebKit(?!.*Safari)/i);
	
		// Pixel Ratio
    device.pixelRatio = window.devicePixelRatio || 1;
	
		// Check for status bar and fullscreen app mode
    var windowWidth = window.innerWidth;
    var windowHeight = window.innerHeight;
    device.statusBar = false;
    if (
        device.webView &&
        (
            // iPhone 5
            (windowWidth === 320 && windowHeight === 568) ||
            (windowWidth === 568 && windowHeight === 320) ||
            // iPhone 4
            (windowWidth === 320 && windowHeight === 480) ||
            (windowWidth === 480 && windowHeight === 320) ||
            // iPad
            (windowWidth === 768 && windowHeight === 1024) ||
            (windowWidth === 1024 && windowHeight === 768)
        )
    ) {
        device.statusBar = true;
    }
    else {
        device.statusBar = false;
    }
        
    // Export object
    return device;
})();

function test(){
	document.write('Device OS:' + device.os + '<br/>');
	document.write('Device OS Version:' + device.osVersion + '<br/>');
	document.write('is iOS:' + device.ios + '<br/>');
	document.write('is iPad:' + device.ipad + '<br/>');
	document.write('is iphone:' + device.iphone + '<br/>');
	document.write('is Android:' + device.android + '<br/>');
	document.write('is WebView:' + device.webView + '<br/>');
	document.write('Pixel Ratio:' + device.pixelRatio + '<br/>');
	document.write('Status Bar:' + device.statusBar + '<br/>');
	
}

test();