Welcome to our next lesson in our TypeScript data structures revision course! Today, we will delve deeply into TypeScript Maps. Much like a bookshelf, Maps allow you to quickly select the book (value) you desire by reading its label (key). They are vital to TypeScript for quickly accessing values using keys, with the added benefit of type safety for efficient key insertion and deletion. So, let's explore TypeScript Maps for a clearer understanding of these concepts and leverage TypeScript's type-checking capabilities.

Our journey starts with TypeScript Maps, a pivotal data structure that holds data as key-value pairs. Imagine storing your friend's contact info in such a way that allows you to search for your friend's name (the key) and instantly find their phone number (the value). To begin working with TypeScript Maps, you initiate an empty Map using the new Map<>() constructor with type annotations to specify the types of keys and values the Map will hold. The first type in the annotation represents the key type, and the second type represents the value type.

In the above code, we create a PhoneBook class that uses a Map to store contacts. As you can see, Maps in TypeScript simplify the processes of adding, modifying, and accessing information with unique keys, all while maintaining type safety. The specific operations involved in utilizing these features will be discussed in the next section.

TypeScript Maps enable a variety of operations for manipulating data, such as setting, getting, deleting key-value pairs, and more. Understanding these operations is crucial for efficient data handling in TypeScript, and type annotations further enhance safety and clarity.

• Add or Update Entries: Use the set method to add a new key-value pair or update an existing key with a new value. This allows dynamic modifications without a predefined structure.

• Retrieve Values: The get method retrieves the value associated with a given key. It returns undefined if the key is not present.

• Check Key Existence: The has method checks whether a specific key exists in the Map, returning true if it does and false otherwise.

• Delete Entries: Utilize the delete method to remove a key-value pair from the Map, aiding in active management of its contents. If the key does not exist, the Map remains unchanged and no error occurs, allowing for safe management of its contents.

• Determine Map Size: The size property provides the total number of key-value pairs currently in the Map.

Let's see how these operations work in the context of a TaskManager class:

This example showcases how to leverage Map operations in TypeScript to effectively manage data by adding, updating, retrieving, deleting entries, and checking the number of entries through a simulated Task Manager application.

TypeScript provides an elegant way to loop through Maps using for...of loops. We can iterate through keys, values, or both simultaneously using specific functions provided by the Map object.

• keys(): This function returns an iterator object containing all the keys in the Map.
• values(): This function returns an iterator object containing all the values in the Map.
• entries(): This function returns an iterator object containing arrays of [key, value] pairs for each entry in the Map.

Let's explore this in our Task Manager example:

In this case, we demonstrate how to use for...of loops with the keys(), values(), and entries() functions to iterate over a Map's keys, values, and entries, respectively. This allows us to flexibly print all tasks in our task manager along with their statuses.

Nesting in Maps involves storing Maps within another Map. It's useful when associating multiple pieces of information with a key. Let's see how this works in a Student Database example.

Let's shift our focus to a more interactive and familiar scenario: managing a shopping cart in an online store. This hands-on example will demonstrate how Maps can be used to map product names to their quantities in a shopping cart. You will learn how to add products, update quantities, and retrieve the total number of items in the cart.

Here’s how you can implement and manipulate a shopping cart using a TypeScript Map:

This example showcases the practical application of Maps to manage a dynamic dataset, such as an online shopping cart. By using product names as keys and their quantities as values, we achieve efficient and flexible data manipulation. This exercise provides a solid foundation for understanding how to handle complex data structures in real-world TypeScript applications.

Well done! Today, we delved into TypeScript Maps and explored various operations, emphasizing the importance of type safety and TypeScript-specific features. We now invite you to get hands-on experience with the upcoming practice exercises. Mastering these concepts and honing your TypeScript Map skills require regular practice. Happy learning!