Reverse mapping in numeric enums in Typescript - Mini Project: Build & Apply

Reverse mapping in numeric enums

📖 Scenario: Imagine you are creating a simple traffic light system in TypeScript. Each light color has a number code. You want to be able to find the color name from the number code and also get the number code from the color name.

🎯 Goal: Build a numeric enum for traffic light colors and use reverse mapping to find the color name from a number code.

📋 What You'll Learn

Create a numeric enum called TrafficLight with exact members: Red = 1, Yellow = 2, Green = 3

Create a variable called lightNumber and set it to 2

Use reverse mapping to get the color name from lightNumber and store it in a variable called lightName

Print the value of lightName to the console

💡 Why This Matters

🌍 Real World

Enums with reverse mapping are useful in programs where you need to convert between codes and names, like traffic lights, status codes, or menu options.

💼 Career

Understanding enums and reverse mapping helps in writing clear and maintainable TypeScript code, a skill valuable for frontend and backend developers working with typed JavaScript.

1

Create the numeric enum

Create a numeric enum called TrafficLight with these exact members and values: Red = 1, Yellow = 2, Green = 3.

Typescript

// Your code here

Need a hint?

Use the enum keyword and assign numbers to each color.

2

Create the number variable

Create a variable called lightNumber and set it to the number 2.

Typescript

enum TrafficLight {
    Red = 1,
    Yellow = 2,
    Green = 3
}

// Your code here

Need a hint?

Use let to create the variable and assign the value 2.

3

Use reverse mapping to get the color name

Use reverse mapping on the TrafficLight enum with lightNumber to get the color name. Store the result in a variable called lightName.

Typescript

enum TrafficLight {
    Red = 1,
    Yellow = 2,
    Green = 3
}

let lightNumber = 2;

// Your code here

Need a hint?

Use bracket notation with the enum and the number variable to get the name.

4

Print the color name

Print the value of lightName to the console using console.log.

Typescript

enum TrafficLight {
    Red = 1,
    Yellow = 2,
    Green = 3
}

let lightNumber = 2;

let lightName = TrafficLight[lightNumber];

// Your code here

Need a hint?

Use console.log(lightName) to show the color name.