Just some notes I took while following along the TypeScript documentation.

InterfaceExamples.ts

//1.0 Interface declared on function

function printBirthday(birthday: { Date: Date, Age: number, Name: string}) {
    console.log(birthday.Name + "'s " + (birthday.Age + 1) + "th birthday"
        + " is on " + birthday.Date + ".");
}

let person = { Name: "Karl", Age: 32, Date: new Date(), Occupation: "Painter" };

printBirthday(person);



//1.1 Interface with optional properties

interface IOrder {
    readonly membership?: string;
    readonly company?: string;
    product: string;
    contactName: string;
    contactPhone: string;
}

interface IPriceReductionSpecification {
    memberReduction: number;
    companyReduction: number;
}

function calculateOrderTotal(order: IOrder, spec: IPriceReductionSpecification) {
    let priceReduction = 0;

    priceReduction += order.membership ? spec.memberReduction : 0;
    priceReduction += order.company ? spec.companyReduction : 0;

    let priceReductionInPercentage = priceReduction / 100;

    let price = order.product == "Claw Hammer" ? 1000 : 0;

    return price - (price * priceReductionInPercentage);
}


//Its optional to explicitly implement an interface

let order1 = {
    product: "Claw Hammer",
    contactName: "Abe Johnson",
    contactPhone: "0734-552198"
};

let order2: IOrder = {
    membership: "Premium",
    company: "Arelius Ink.",
    product: "Claw Hammer",
    contactName: "Marcus Arelius",
    contactPhone: "0724-122430"
};

let priceReductionSpecification = {
    memberReduction: 10,
    companyReduction: 10
};


console.log("Full price: " + calculateOrderTotal(order1, priceReductionSpecification));
console.log("Reduced price: " + calculateOrderTotal(order2, priceReductionSpecification));


//1.2 Readonly Array

let numbers: ReadonlyArray<number> = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];