Why enums are needed in Typescript - See It in Action

Why enums are needed

📖 Scenario: Imagine you are building a simple app that tracks the status of orders in a store. Each order can be in one of a few fixed states like Pending, Shipped, or Delivered. You want to keep your code clear and avoid mistakes when using these states.

🎯 Goal: You will create a TypeScript enum to represent order statuses. Then you will use this enum to check and print the status of an order. This helps keep your code easy to read and prevents errors from using wrong status values.

📋 What You'll Learn

Create an enum called OrderStatus with values Pending, Shipped, and Delivered

Create a variable called currentStatus and set it to OrderStatus.Pending

Write an if statement to check if currentStatus is OrderStatus.Shipped

Print a message showing the current order status using the enum

💡 Why This Matters

🌍 Real World

Enums are used in apps to represent fixed sets of options like order statuses, user roles, or colors.

💼 Career

Understanding enums helps you write safer and clearer code, a skill valued in many programming jobs.

1

Create the enum for order statuses

Create an enum called OrderStatus with these exact members: Pending, Shipped, and Delivered.

Typescript

# Your code here

Hint

An enum groups related named values. Use enum OrderStatus { Pending, Shipped, Delivered }.

2

Set the current order status

Create a variable called currentStatus and set it to OrderStatus.Pending.

Typescript

enum OrderStatus {
    Pending,
    Shipped,
    Delivered
}

# Your code here

Hint

Use let currentStatus = OrderStatus.Pending; to assign the enum value.

3

Check if the order is shipped

Write an if statement that checks if currentStatus is equal to OrderStatus.Shipped.

Typescript

enum OrderStatus {
    Pending,
    Shipped,
    Delivered
}

let currentStatus = OrderStatus.Pending;

# Your code here

Hint

Use if (currentStatus === OrderStatus.Shipped) { ... } to compare enum values.

4

Print the current order status

Print the message The current order status is: Pending by using console.log and the enum value OrderStatus.Pending.

Typescript

enum OrderStatus {
    Pending,
    Shipped,
    Delivered
}

let currentStatus = OrderStatus.Pending;

if (currentStatus === OrderStatus.Shipped) {
    console.log("The order has been shipped.");
}

# Your code here

Hint

Use console.log(`The current order status is: ${OrderStatus[currentStatus]}`); to print the status name.

Practice

1. Why are enums useful in TypeScript?
enum Color { Red, Green, Blue }

easy

A. They group related values with readable names.

B. They allow dynamic addition of new values at runtime.

C. They replace all functions in TypeScript.

D. They automatically convert numbers to strings.

Solution

1. Step 1: Understand what enums represent

   Enums group a fixed set of related values under friendly names, improving code clarity.

2. Step 2: Analyze the options

   Only They group related values with readable names. correctly describes enums' purpose. Options A, B, and C are incorrect features.

3. Final Answer:

   They group related values with readable names. -> Option A

4. Quick Check:

   Enums improve readability = D [OK]

Hint: Enums group fixed options with names, not dynamic values [OK]

Common Mistakes:

• Thinking enums allow adding values at runtime
• Confusing enums with functions
• Believing enums convert numbers to strings automatically

2. Which of the following is the correct syntax to declare an enum in TypeScript?

easy

A. enum Direction { Up, Down, Left, Right }

B. enum Direction = (Up, Down, Left, Right);

C. enum Direction: [Up, Down, Left, Right];

D. enum Direction { 'Up', 'Down', 'Left', 'Right' }

Solution

1. Step 1: Recall enum declaration syntax

   In TypeScript, enums are declared using the keyword enum followed by curly braces with comma-separated names.

2. Step 2: Check each option

   enum Direction { Up, Down, Left, Right } matches the correct syntax. Options A and C use invalid assignment or colon syntax. enum Direction { 'Up', 'Down', 'Left', 'Right' } incorrectly uses quotes around names.

3. Final Answer:

   enum Direction { Up, Down, Left, Right } -> Option A

4. Quick Check:

   Correct enum syntax uses braces and names without quotes = B [OK]

Hint: Enums use braces and names without quotes [OK]

Common Mistakes:

• Using equals sign or colon instead of braces
• Putting quotes around enum member names
• Ending enum declaration with semicolon incorrectly

3. What will be the output of this TypeScript code?

enum Status { Active = 1, Inactive, Pending }
console.log(Status.Inactive);

medium

A. Inactive

B. 1

C. 0

D. 2

Solution

1. Step 1: Understand enum numeric values

   The enum starts with Active = 1, so Inactive gets the next number, 2, and Pending gets 3.

2. Step 2: Check the logged value

   Logging Status.Inactive prints its numeric value, which is 2.

3. Final Answer:

   2 -> Option D

4. Quick Check:

   Enum auto-increments numbers = A [OK]

Hint: Enum numbers auto-increment from first assigned value [OK]

Common Mistakes:

• Assuming enum starts at 0 when first value is assigned 1
• Expecting string output instead of number
• Confusing enum member names with their values

4. Identify the error in this enum declaration:

enum Size {
  Small = 'S',
  Medium = 'M',
  Large = 3
}

medium

A. Enum values must be unique numbers only.

B. Mixing string and number values in one enum is not allowed.

C. Enum member names must be lowercase.

D. Missing semicolon after enum declaration.

Solution

1. Step 1: Check enum value types

   TypeScript enums can be numeric or string, but mixing both types in one enum causes errors.

2. Step 2: Analyze the given enum

   Here, 'Small' and 'Medium' have string values, but 'Large' has a number, which is invalid.

3. Final Answer:

   Mixing string and number values in one enum is not allowed. -> Option B

4. Quick Check:

   Enum values must be consistent type = C [OK]

Hint: Enum values must be all strings or all numbers [OK]

Common Mistakes:

• Thinking enum member names must be lowercase
• Believing enum values must be unique numbers only
• Assuming missing semicolon causes error

5. You want to represent fixed user roles in your app: 'Admin', 'Editor', and 'Viewer'. Why is using an enum better than plain strings?

enum UserRole { Admin, Editor, Viewer }

hard

A. Enums automatically encrypt role names for security.

B. Enums allow adding new roles dynamically at runtime.

C. Enums prevent typos and make code easier to maintain.

D. Enums convert roles to numbers for faster database storage.

Solution

1. Step 1: Understand the benefit of enums for fixed sets

   Enums provide named constants that prevent typos and improve readability and maintainability.

2. Step 2: Evaluate the options

   Enums prevent typos and make code easier to maintain. correctly states the main advantage. Options B, C, and D describe incorrect or unrelated features.

3. Final Answer:

   Enums prevent typos and make code easier to maintain. -> Option C

4. Quick Check:

   Enums improve safety and clarity = A [OK]

Hint: Enums reduce errors by using fixed named values [OK]

Common Mistakes:

• Believing enums add dynamic behavior
• Thinking enums provide encryption
• Assuming enums optimize database storage automatically