var ClockSkew = require('clockskew/client');
// or just include the file 

var clockSkew = new ClockSkew({
	// REQUIRED :
	getServerTime: ClockSkew.getSocketTime('ws://...'),
	// or use HTTP protocol
	getServerTime: ClockSkew.getHttpTime.bind(null,'http://'),
	// or use Firebase
	getServerTime: ClockSkew.getFirebaseTime.bind(null,'https://xxx.firebaseio.com/timestamp')

	// OPTIONAL:
	getTime: function(){...}, // get local time in ms.
	timeout: 10000, // ping timeout
	interval: 1000, // ping interval
	history: 10, 
	tolerance: 2, // is standard deviation of last `history` average skew is less then tolerance, wait longer before pinging.
	waitInteval: 30000, // wait interval
	minSkewValues: 5, // minimum values before averaging
	minRttValues: 5 // minimum Round-Trip-Time values before rejecting RTTs that are more than 1 standard deviation slower
	setTimeout: ... // custom setTimeout Implementation
	clearTimeout: ... // custom clearTimeout implementation
	onSkew: function(skew) { // do stuff },
});

clockSkew.start();
clockSkew.stop();
clockSkew.skew;