Cutting the Mustard Feature Detection

mustard.js

// From: http://responsivenews.co.uk/post/18948466399/cutting-the-mustard
if('querySelector' in document && 'localStorage' in window && 'addEventListener' in window) {
    // Load the enhanced app:
    /*
    HTML5 browsers:-
    IE9+
    Firefox 3.5+
    Opera 9+ (and probably further back)
    Safari 4+
    Chrome 1+ (I think)
    iPhone and iPad iOS1+
    Android phone and tablets 2.1+
    Blackberry OS6+
    Windows 7.5+ (new Mango version)
    Mobile Firefox (all the versions we tested)
    Opera Mobile (all the versions we tested)
    */
}
else {
    // Load the basic app:
    /*
    HTML4 browsers:-
    IE8-
    Blackberry OS5-
    Nokia S60 v6-
    Nokia S40 (all versions)
    All other Symbian variants
    Windows 7 phone (pre-Mango)
    …and many more that are too numerous to mention
    */
}

new-mustard.js

// From: https://justmarkup.com/log/2015/02/26/cut-the-mustard-revisited/
if ('visibilityState' in document) { 
	// Modern browser. Let's load JavaScript
	if ('serviceWorker' in navigator) {
		// Let's add offline support
		navigator.serviceWorker.register('sw.js', {
			scope: './'
		});
	}
}