Storing State in Functions

1-new-constructor.js

/*

Typical prototypical pattern. Store all state, configuration, and functions on the "this" object.

*/

var Car = function( engineType ) {
	
	this.engine = engineType || "v4";
	this.timesRevved = 0;
	
};

Car.prototype = {
	
	rev : function() {
		
		this.timesRevved++;
		
		switch( this.engine ) {
			case "v8":
				console.log("vrooooooooom!");
				break;
			case "v6":
				console.log("vroooom");
				break;
			default:
				console.log("vroom");
				
		}
	}
	
};

var car = new Car( "v8" );
car.rev();

//Mutate
car.engine = "v6";
car.rev();

2-bound-state.js

function engineRever() {
	
	this.state.timesRevved++;
	
	switch( this.engine ) {
		case "v8":
			console.log("vrooooooooom!");
			break;
		case "v6":
			console.log("vroooom");
			break;
		default:
			console.log("vroom");
	}
	
}

var car = function( privateEngine ) {
	
	var state = {
		timesRevved: 0
	};
	
	return {
		rev : engineRever.bind({
			engine : privateEngine,
			state : state
		}),
		timesRevved : function() { return state.timesRevved }
	};
	
};


var normalCar = car( "v6" );
normalCar.rev();

var fastCar = car( "v8" );
fastCar.rev();

3-state-in-closure.js

function engineRever( state, engine ) {
	
	state.timesRevved++;
	
	return function rev() {
		
		switch( engine ) {
			case "v8":
				console.log("vrooooooooom!");
				break;
			case "v6":
				console.log("vroooom");
				break;
			default:
				console.log("vroom");
		}	
	}
}

var car = function( engine ) {
	
	var state = {
		timesRevved: 0
	};
	
	return {
		rev : engineRever( state, engine ),
		timesRevved : function() { return state.timesRevved }
	};
	
};


var normalCar = car( "v6" );
console.log( normalCar.timesRevved() );
normalCar.rev();
console.log( normalCar.timesRevved() );

var fastCar = car( "v8" );
fastCar.rev();
fastCar.rev();
console.log( fastCar.timesRevved() );