1. Contents
  2. 27. TypeScript
  3. 27.3. Arrays in TypeScript

27.3. Arrays in TypeScript

Arrays in TypeScript must contain values of the same type. When declaring an array, the type needs to be declared.

1let arrayName: number[] = [10,9,8];

What if the array needs to hold values of different types?

Now, we need a tuple. A tuple is a special structure in TypeScript that can hold as many values as needed of different types.

1let tupleName: [number, string, number];
2
3tupleName = [10, "9", 8];

27.3.1. Examples

In JavaScript, we would declare an array holding items in our cargo hold like so:

let cargoHold = ['oxygen tanks', 'space suits', 'parrot', 'instruction manual', 'meal packs', 'slinky', 'security blanket'];

In TypeScript, we would declare the same cargoHold array a little differently:

let cargoHold: string[] = ['oxygen tanks', 'space suits', 'parrot', 'instruction manual', 'meal packs', 'slinky', 'security blanket'];

What about declaring arrays for elements on the Periodic Table? In JavaScript, that is a relatively simple task:

1let element1 = ['hydrogen', 'H', 1.008];
2let element2 = ['helium', 'He', 4.003];
3let element26 = ['iron', 'Fe', 55.85];

In TypeScript, however, an array can only hold values of one type, so we need to use a tuple.

1let element1: [string, string, number];
2element1 = ['hydrogen', 'H', 1.008];
3
4let element2: [string, string, number];
5element2 = ['helium', 'He', 4.003];
6
7let element26: [string, string, number];
8element26 = ['iron', 'Fe', 55.85];

27.3.2. Check Your Understanding

Question

Which of the following statements is FALSE about a tuple in TypeScript?

  1. Tuples can hold as many elements as needed.
  2. Tuples hold values of one type.
  3. When declaring a tuple, programmers include the types of the values in a tuple.