builder pattern in TypeScript

builderPattern.ts

interface BurgerBoy {
	size: number;
	cheese: boolean;
	pepperoni: boolean;
	lettuce: boolean;
	tomato: boolean;
	addPepperoni(): any;
	addCheese(): any;
	addLettuce(): any;
	addTomato(): any;
	build(): any;
}

type size = number;
type cheese = boolean;
type pepperoni = boolean;
type lettuce = boolean;
type tomato = boolean;
type extras = string;

class Burger {
	private size: size;

	private cheese: cheese = false;
	private pepperoni: pepperoni = false;
	private lettuce: lettuce = false;
	private tomato: tomato = false;

	constructor(builder) {
		this.size = builder.size;
		this.cheese = builder.cheese;
		this.pepperoni = builder.pepperoni;
		this.lettuce = builder.lettuce;
		this.tomato = builder.tomato;
	}
}

class BurgerBuilder implements BurgerBoy {

	public size: size;

	public extras: extras;
	public cheese: cheese = false;
	public pepperoni: pepperoni = false;
	public lettuce: lettuce = false;
	public tomato: tomato = false;

	constructor(size: number) {
		this.size = size;
	}

	public addPepperoni(): any {
		this.pepperoni = true;
		return this;
	}

	public addLettuce(): any {
		this.lettuce = true;
		return this;
	}

	public addCheese(): any {
		this.cheese = true;
		return this;
	}

	public addTomato(): any {
		this.tomato = true;
		return this;
	}

	public addExtras(extras: string[]): any {
		this.extras = BurgerBuilder.createExtrasString(extras);
		return this;
	}

	public build(): any {
		return new Burger(this);
	}

	private static createExtrasString(extras: string[]): string {
		return extras.join();
	}

}

const newBurger = new BurgerBuilder(14).addPepperoni().addCheese().addLettuce().addTomato().addExtras(['onion', 'peppers']).build();

console.dir(newBurger);