Checking a white list of supported browsers for javascript applications

whitelist.js

(function (agent) {
	var whiteList = { // example of a whitelist. browser name/version and a UA substring
		"firefox31"  : "Firefox/31.0",
		"IE10"       : "MSIE 10.0",
		"chrome37"   : "Chrome/37",
		"chrome38"   : "Chrome/38",
		"chrome39"   : "Chrome/39"
	}, validBrowser = false;
	
	for(var browser in whiteList){
		if(agent.indexOf(whiteList[browser]) > -1){
			validBrowser = true;
			break;
		}
	}
	if(!validBrowser){
		// You're not supporting this browser. Do something.
	}
})(navigator.userAgent);

/*
 * N.b. While user agent strings can not always be trusted, something you need to sniff the UA string.
 * (Yeah, yeah feature detection and all that but sometimes no because of reasons)
 */