TypeScript Union

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TypeScript is a superset of JavaScript that adds types to JavaScript. With TypeScript, we can define the type of variables, functions, and parameters. In TypeScript, a union type is a type formed by combining two or more other types. In this lesson, we will discuss TypeScript union in detail with a code example.

What is TypeScript Union?

A union type in TypeScript is a type that can represent values of multiple types. It is formed by using the vertical bar | to separate the types. For example, the union type string | number represents a type that can hold either a string or a number.

Union types are useful when a function or a variable can accept different types of input. They allow us to define more flexible types that can handle different types of data.

Syntax of TypeScript Union

The syntax for defining a union type in TypeScript is:

type UnionType = Type1 | Type2 | Type3 | ... | TypeN;

where Type1, Type2, Type3, …, TypeN are the types that are being combined.

TypeScript Union Example

Let’s look at an example of using a union type in TypeScript. Suppose we want to create a function that can accept either a string or a number as its parameter.

function printData(data: string | number): void {
  console.log(data);
}

printData("Hello, TypeScript!"); // Output: Hello, TypeScript!
printData(123); // Output: 123

In the above code, we defined a function printData that takes a parameter data of type string | number. The function simply logs the value of data to the console.

We then called the printData function with a string argument and a number argument. In both cases, the function was able to handle the input correctly because of the union type.

Conclusion

In conclusion, TypeScript union is a powerful feature that allows us to define more flexible types in TypeScript. By combining multiple types using the vertical bar |, we can create a union type that can hold values of different types. Union types are useful when we need to define a variable, function, or parameter that can accept different types of input.