1. Declaration of Arrays

   • Using Square Brackets: You can declare an array using the square brackets [] syntax.

     let fruits: string[] = ['Apple', 'Banana', 'Cherry'];

   • Using Generic Array Type: Alternatively, you can use the Array<elementType> syntax.

     let fruits: Array<string> = ['Apple', 'Banana', 'Cherry'];

2. Initialization of Arrays

   • Arrays can be declared and initialized simultaneously:

     let numbers: number[] = [1, 2, 3, 4];

   • You can also declare an array without initialization and assign values later:

     let colors: string[];
     colors = ['Red', 'Green', 'Blue'];

3. Mixed Data Types

   • TypeScript allows arrays to contain elements of different types using union types.

     let mixedArray: (string | number)[] = ['Alice', 25, 'Bob', 30];

4. Accessing Array Elements:

   • You can access elements using their index (zero-based).

     let firstFruit = fruits[0]; // 'Apple'

5. Modifying Arrays

   • You can add elements to an array using the push() method.

     fruits.push('Mango'); // Adds 'Mango' to the end of the array

   • You can remove elements using the pop() method.

     let lastFruit = fruits.pop(); // Removes and returns the last element

6. Array Properties and Methods

   • Length Property: The length property returns the number of elements in an array.

     console.log(fruits.length); // Outputs: number of elements in fruits array

   • Common Methods:
     • forEach(): Executes a provided function once for each array element.

       fruits.forEach(fruit => console.log(fruit));

     • map(): Creates a new array with the results of calling a provided function on every element.

       let upperCaseFruits = fruits.map(fruit => fruit.toUpperCase());

     • filter(): Creates a new array with all elements that pass the test implemented by the provided function.

       let longFruits = fruits.filter(fruit => fruit.length > 5);

7. Readonly Arrays

   • You can create arrays that cannot be modified using the readonly modifier.
     

     const readonlyFruits: readonly string[] = ['Apple', 'Banana'];
     //readonlyFruits.push('Cherry'); // Error: Property 'push' does not exist on type 'readonly string[]'.

8. Array Type Inference

   • TypeScript can infer the type of an array based on its initial values.
     

     const numbers = [1, 2, 3]; // Inferred as number[]
     numbers.push(4); // No error
     // numbers.push("5"); // Error: Argument of type 'string' is not assignable to parameter of type 'number'.

Conclusion

• TypeScript arrays are versatile and provide powerful typing capabilities that improve code quality and maintainability.
• By understanding how to declare, initialize, access, and manipulate arrays, you can use them to their full potential in your TypeScript applications.