Union Types

Union types allow a variable to hold one of several types using the | operator.

Syntax

TYPESCRIPT

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let id: string | number;
id = "ABC123";
id = 123;

Union and Literal Types

TYPESCRIPT

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type ID = string | number;

function printId(id: ID): void {
    console.log(`ID: ${id}`);
}

printId(101);
printId("abc-123");

type Direction = "up" | "down" | "left" | "right";

function move(dir: Direction): void {
    console.log(`Moving ${dir}`);
}

move("up");

Try It Yourself

Practice

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Exercise

Practice this concept.

Answer

Write the code as shown above.

Quick Quiz

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What did you learn?

Concept A

Concept B

Concept C

Concept D

This covers the basics.

Retry Quiz

Interview Questions

Explain this concept.

It is a fundamental TypeScript feature.

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