Tuples and Enums

oghenekparobo StephenFebruary 8, 2025About 2 min

Tuples and Enums 관련

Learn TypeScript – A Handbook for Developers

This handbook will teach you the basics of TypeScript, including what it is, why it is useful, and the key features it offers. TypeScript was created by Anders Hejlsberg, a prominent software engineer at Microsoft who’s also known for his work on C# ...

Learn TypeScript – A Handbook for Developers

Tuple

A tuple in TypeScript is a special type of array that has a fixed number of elements, where each element can have a different type. Tuples ensure that the order and types of values remain consistent.

// A tuple with a string and a number
let user: [string, number] = ["Alice", 25];

console.log(user[0]); // Output: Alice
console.log(user[1]); // Output: 25

In this example, the tuple user contains a string (name) and a number (age). The order and types must be followed as defined.

Tuple with Optional Elements:

let person: [string, number, boolean?] = ["Bob", 30];

console.log(person); // Output: ["Bob", 30]

Here, the third element (boolean) is optional.

Tuple with Read-Only Property:

const coordinates: readonly [number, number] = [10, 20];

// coordinates[0] = 50; // Error: Cannot assign to '0' because it is a read-only tuple

The readonly keyword prevents modifying tuple values.

Enums

An enum in TypeScript is a way to define a set of named constants. Enums make code more readable and help manage a fixed set of values.

Numeric Enums (Default):

enum Status {
  Pending,   // 0
  InProgress, // 1
  Completed,  // 2
}

console.log(Status.Pending);   // Output: 0
console.log(Status.Completed); // Output: 2

By default, TypeScript assigns numeric values starting from 0.

Custom Number Values in Enums

enum OrderStatus {
  Pending = 1,
  Shipped = 5,
  Delivered = 10,
}

console.log(OrderStatus.Shipped); // Output: 5

Here, custom values are assigned to each status.

String Enums

enum Direction {
  Up = "UP",
  Down = "DOWN",
  Left = "LEFT",
  Right = "RIGHT",
}

console.log(Direction.Up); // Output: "UP"

String enums store fixed text values instead of numbers.

Using Enums in a Function:

function getStatusText(status: Status): string {
  switch (status) {
    case Status.Pending:
      return "Order is pending.";
    case Status.InProgress:
      return "Order is in progress.";
    case Status.Completed:
      return "Order is completed.";
    default:
      return "Unknown status.";
  }
}

console.log(getStatusText(Status.InProgress)); // Output: "Order is in progress."

This function takes an enum value and returns a message based on the status.

Tuples define fixed-length arrays with different data types, while enums provide named constants for better readability, making your code more structured and type-safe.