TypeScript, like JavaScript, allows you to work with arrays of values. Type annotations are used to enforce type checking. Array types can be written in one of two ways. In the first, you use the type of the elements followed by [] to denote an array of that element type: let list: number[] = [1, 2, 3]; The second way uses a generic array type, Array
: let list: Array = [1, 2, 3]; It is not mandatory in TypeScript to use type annotations. However, type annotations help the compiler in checking types and helps avoid errors dealing with data types. It is also a good way of writing code for easier readability and maintenance by future developers working on your code.