usefulness.js

function price() {
	return this.price;
}

function howMuchIsIt() {
	var ans = "It's "  + price.call( this ) + ' worth';
	console.log( ans );
}

var productA = {
	price: "$150"
};

var productB = {
	price: "$200"
};

price.call( productA ); // $150
price.call( productB ); // $200

howMuchIsIt.call( productA ); // It's $150 worth
howMuchIsIt.call( productB ); // It's $200 worth