ES5 example of 'this' scope using 'self' variable

gistfile1.js

function Gamer() {
	// Store value of this in a variable
	var self = this; // Some people use that or _this
	self.playTime = 0;
	
	// trackPlayTime() will now correctly auto increment every second
	setInterval( function trackPlayTime() {
		// Because we're using a variable we don't have to worry about the dynamic value of this in the new function scope
		self.playTime++;
		// Correctly out
		console.log( self.playTime ); 
	}, 1000 );
}

var gamer = new Gamer();