An example showing how to create a function that must call its pre-requisites in order to be called, using TypeScript.

PizzaBuilder.ts

// Let's create a class to build a simple Pizza
// Our PizzaBuilder can set:
// 1. Pizza size (required)
// 2. Pizza flavour (required)
// 3. Pizza crust (optional)
// We must make sure that the "cook" function is type-checked and can be called
// only if we have set a size or a flavour.

type PizzaSizes = 'small' | 'medium' | 'large' | 'extra large';
type PizzaFlavour = 'pepperoni' | 'bbq chicken' | 'margherita' | 'vegetarian';
type PizzaCrust = 'classic' | 'cheesy' | 'edge';

type PizzaBuilderType = {
    size: PizzaSizes
    flavour: PizzaFlavour
    crust?: PizzaCrust
};

class PizzaBuilder {
    size?: PizzaSizes
    flavour?: PizzaFlavour
    crust?: PizzaCrust

    setSize(size: PizzaSizes): this & Pick<PizzaBuilderType, 'size'> {
        return Object.assign(this, { size });
    }

    setFlavour(flavour: PizzaFlavour): this & Pick<PizzaBuilderType, 'flavour'> {
        return Object.assign(this, { flavour });
    }

    setCrust(crust: PizzaCrust): this & Pick<PizzaBuilderType, 'crust'> {
        return Object.assign(this, { crust });
    }

    cook(this: PizzaBuilderType): object {
        return { size: this.size, flavour: this.flavour, crust: this.crust };
    }
}

const pepperoniPizza = new PizzaBuilder().setSize('small').setFlavour('pepperoni').cook();

// Uncomment the line below, the type-checker won't let you call the cook() method, as the flavour is missing.
// const invalidPizza = new PizzaBuilder().setSize('small').cook();