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TypeScript Aliases
TypeScript: Type Aliases
Type aliases let you create your own names for types — to make code easier to read and reuse.
What’s a Type Alias?
Think of a type alias like a shortcut.
Instead of writing the same type over and over, you give it a custom name.
It helps simplify long or complex type definitions.
How to Make One
Use the type keyword followed by your chosen name:
type ID = string | number;
Now, instead of repeating string | number everywhere, just use ID:
let userId: ID = 101; let postId: ID = "a1b2";
Both are valid because ID allows either a string or a number.
Useful with Objects Too
type Book = {
title: string;
pages: number;
isAvailable: boolean;
};
let myBook: Book = {
title: "Clean Code",
pages: 464,
isAvailable: true
};
Aliases in Functions
They can also define input or return types in functions:
type Status = "pending" | "success" | "failed";
function updateStatus(status: Status) {
console.log("Status:", status);
}
Now the function only accepts those specific strings.
When to Use Type Aliases
- When a type is long or repeated
- For union or literal types
- To make your code self-explanatory
- To give structure to objects without using interfaces
Type Alias vs Interface
They can feel similar, but:
- type can describe unions, primitives, functions, and tuples
- interface is better for extending and organizing objects
Use what feels more readable — and remember, you can often choose either!
Prefer Learning by Watching?
Watch these YouTube tutorials to understand TYPESCRIPT Tutorial visually:
What You'll Learn:
- 📌 TypeScript Tutorial #9 Type Aliases
- 📌 Explained in 2 Minutes: Type vs Interface In Typescript