Typescript String Based Enums Examples

In TypeScript, enums are set of named constants. Though it is optional, enums should be a named group of related constants.

5 Typescript String-based Enums Examples

In a string enum, each member has to be constant-initialized with a string literal, or with another string enum member.

Example 1: How to create enum in Typescript

Let's create a typescript file named enums.ts and add following code to it:

// Example 2 - String-based Enums
enum Direction {
    Up = "UP",
    Down = "DOWN",
    Left = "LEFT",
    Right = "RIGHT",
}

// Access enum member values
console.log(Direction.Up);
console.log(Direction.Down);
console.log(Direction.Left);
console.log(Direction.Right);

console.log(Direction['Up']);
console.log(Direction['Down']);

Example 2: How to access enum member values

Use Enum.member or Enum['member'] format to access enum member values. For Example:

console.log(Direction.Up);
console.log(Direction.Down);
console.log(Direction['Up']);
console.log(Direction['Down']);

Let's run above typescript file using the following command:

c:\user\typescript-tutorial> tsc .\enums.ts

Look at the generated code in JavaScript. It has a generated lookup table like this.

var Direction;
(function (Direction) {
    Direction["Up"] = "UP";
    Direction["Down"] = "DOWN";
    Direction["Left"] = "LEFT";
    Direction["Right"] = "RIGHT";
})(Direction || (Direction = {}));
// Access enum member values
console.log(Direction.Up);
console.log(Direction.Down);
console.log(Direction.Left);
console.log(Direction.Right);
console.log(Direction['Up']);
console.log(Direction['Down']);

The above file created as enums.js file. Now we don't need a browser, we can use node.js to run this javascript file. Let's run this enums.js file using the following command:

c:\user\typescript-tutorial> node .\enums.js
UP
DOWN
LEFT
RIGHT
UP
DOWN

Follow similar steps to run below typescript examples.

Example 3: LogLevel Enum

// Example 1- String-based Enums
export enum LogLevel {
    Off = "Off",
    Fatal = "Fatal",
    Error = "Error",
    Warn = "Warn",
    Info = "Info",
    Debug = "Debug"
}

// Access enum member values
console.log(LogLevel.Debug);
console.log(LogLevel.Error);
console.log(LogLevel.Warn);
console.log(LogLevel.Info);
console.log(LogLevel.Fatal);

console.log(LogLevel['Fatal']);
console.log(LogLevel['Debug']);
console.log(LogLevel['Info']);

Example 4: Weekday Enum

// Example 3 - String-based Enums
enum Weekday {
    Monday = "Monday",
    Tuesday = "Tuesday",
    Wednesday = "Wednesday",
    Thursday = "Thursday",
    Friday = "Friday",
    Saturday = "Saturday",
    Sunday = "Sunday"
}

// Access enum member values
console.log(Weekday.Monday);
console.log(Weekday.Tuesday);
console.log(Weekday.Wednesday);
console.log(Weekday.Thursday);
console.log(Weekday.Friday);
console.log(Weekday.Saturday);
console.log(Weekday.Sunday);

console.log(Weekday['Saturday']);
console.log(Weekday['Sunday']);

Example 5: Enum as a function argument

To pass enum in functions, declare the argument type of enum itself.

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

function checkDirection(direction: Direction){
    console.log(direction);
}

checkDirection(Direction.Up);
checkDirection(Direction.Down);
checkDirection(Direction.Left);
checkDirection(Direction.Right);

Output:

C:\user\typescript-tutorial> tsc .\enums.js
C:\user\typescript-tutorial> node .\enums.js
UP
DOWN
LEFT
RIGHT

Reference

https://www.javaguides.net/2019/09/typescript-enums-tutorial-with-examples.html