Welcome to our exploration of Compound Data Structures in TypeScript. Having navigated through Maps, Sets, and Arrays, we'll delve into Nested Maps and Nested Arrays. These structures enable us to handle complex and hierarchical data, which is typical in real-world scenarios. Nested data structures are commonly used to represent data models like organizational charts, product categories, and multi-dimensional datasets. This lesson will guide you through a recap of the basics, as well as the creation and modification of nested Maps and Arrays.

As a quick recap, Arrays are mutable, ordered collections, while Maps are collections of key-value pairs with maintained insertion order. These structures can be nested. Here's a simple example of a school directory:

Just like their non-nested versions, creating nested structures is straightforward, with added type safety in TypeScript.

Nested Map:

Nested Array:

Nested Maps and Arrays:

The retrieval of values from nested Maps or arrays is facilitated by TypeScript's type-checking, which ensures that operations are performed on valid structures.

From Nested Map:

In this code example, the optional chaining operator (?.) is used in nestedMap.get('fruit')?.get('apple') to avoid errors:

• nestedMap.get('fruit') attempts to access the nested Map associated with the 'fruit' key.
• The ?. operator ensures that if 'fruit' does not exist (i.e., returns undefined), it does not attempt to call .get('apple'), which would cause an error.
• Instead, the expression safely evaluates to undefined if 'fruit' is missing, preventing a runtime error.
• If 'fruit' is present, then .get('apple') executes normally, retrieving the color 'red'.

From Nested Array:

From Both:

While retrieving data from nested Maps or arrays, it's important to handle potential errors gracefully. This can be done using conditional checks or try-catch blocks.

Error Handling with Nested Maps and Arrays:

For nested Maps and arrays, check the existence of keys and valid indices.

Using try-catch for Error Handling:

Alternatively, you can use try-catch blocks to handle errors.

By implementing these error handling techniques, you can ensure your code is more robust and resilient against common issues with nested data structures.

Modification of nested arrays and Maps is similar to non-nested versions, and TypeScript ensures that these operations conform to defined types.

Bravo! You've made a journey through nested arrays and Maps, terms that are becoming increasingly common in the data-intensive programming world. We've learned how to create, access, and modify values in these complex structures using TypeScript to ensure type safety and prevent errors. Up next, we have hands-on practice sessions to solidify your understanding of these concepts. Hold on to your hats!