Array, Tuple, Union in TypeScript

Array:

Array use of variables to store values. 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.

Declaring and Initializing Arrays       

To declare an initialize an array in Typescript uses the following syntax:

let arrayName:datatype[]  //declaration

arrayName=[1,2,3]  //initialization

many way array declaration

 

Tuple:

We know that an array holds multiple values of the same datatype. But sometimes, we may need to store a collection of values of different data types in a single variable. Arrays will not provide this feature, but TypeScript has datatype called tuple to achieve this purpose.

We may want to represent a value as a pair of a string and a number:

Declare a tuple type

Initialize it

Initialize it incorrectly

Accessing an element outside the set of known indices fails with an error:

Destructuring a Tuple

Union:

we can define a variable that can have multiple types of values. Two or more data types are combined using the pipe symbol (|) to denote a Union Type. In other words, a union type is written as a sequence of types separated by vertical bars.

Example: Union Type Variable

 

Reference: https://www.typescriptlang.org/docs/handbook/basic-types.html https://www.javatpoint.com/