Learn TypeScript 3 by Building Web Applications

Numerical enums

Numerical enums are the simplest way to define enumerations (or enums) in TypeScript. Each entry in such an enum simply associates a logical name with a numerical value.

The following is a basic example of a numerical enum:

enum VehicleType { 
    Car, 
    Bus, 
    Train 
} 
 
let myVehicleType = VehicleType.Car; 
console.log("My vehicle type: ", myVehicleType); 

And the following is the corresponding output:

$ node ts-enums-01.js 
My vehicle type:  0 

As you can see, in their basic form, enum entries map to unsigned integer values that start at 0.

As you can guess, reordering entries in a numerical enum has an immediate impact on the associated values. This matters a lot if you persist those values somehow, as you will get different results ...