How to Declare an Empty Array in TypeScript?

TypeScript provides a robust type system that allows you to define and manage data structures more effectively than in plain JavaScript. One common task is declaring empty arrays with specific types, ensuring that your array holds only values of the intended type.

These are the following ways to declare an empty array in TypeScript:

Declaring an Empty Array of a Specific Type

In TypeScript, you can declare an empty array that will only accept elements of a particular type. The most common approach is using the square bracket syntax to specify the type of the array. This ensures that only numbers can be added to the numbers array. Trying to add a value of a different type (e.g., a string) will result in a compilation error.

Example: In this example, we will declare an empty array of numbers that can only hold numbers.

let numbers: number[] = [];
numbers.push(1);
numbers.push(2);

console.log(numbers);
// Output: [1, 2]

Output:

[1, 2]

Declaring an Array That Can Hold Multiple Types

Sometimes you may need an array that can store values of different types. TypeScript allows you to use union types to declare such arrays. This approach is useful when you need a flexible array that can store different types of data, but you still want the type safety provided by TypeScript.

Example: In this example, the array can hold both numbers and strings.

let mixedArray: (number | string)[] = [];
mixedArray.push(1);
mixedArray.push("Hello");

console.log(mixedArray); 
// Output: [1, "Hello"]

Output:

[1, "Hello"]