Template Literal Types

Template Event Names

Template literal types describe strings that are assembled from smaller sets of names.

template literal type A type such as `` `${Entity}:${Action}` `` keeps event names aligned with the allowed pieces.

Template Event Names

entity
event_names.ts
Replay: real traced execution (multi-file project)
type Entity = "user" | "order";
type Action = "created" | "updated";
type EventName = `${Entity}:${Action}`;

function publish(eventName: EventName): string {
    return `publish ${eventName}`;
}

const entity: Entity = "user";
const action: Action = "created";
const eventName: EventName = `${entity}:${action}`;

console.log(publish(eventName));

type Entity = "user" | "order";
type Action = "created" | "updated";
type EventName = `${Entity}:${Action}`;

function publish(eventName: EventName): string {
    return `publish ${eventName}`;
}

const entity: Entity = "order";
const action: Action = "created";
const eventName: EventName = `${entity}:${action}`;

console.log(publish(eventName));

  1. entity ← user, action ← created, eventName ← user:created

    6    return `publish ${eventName}`;7}89const entity→ user: Entity = "user";  //@entity="order"10const action→ created: Action = "created";11const eventName→ user:created: EventName = `${entityuser}:${actioncreated}`;1213console.log(publish(eventNameuser:created));

  2. function publish(eventName: EventName): string

    2type Action = "created" | "updated";3type EventName = `${Entity}:${Action}`;45function publish(eventNameuser:created: EventName): string {6    return `publish ${eventNameuser:created}`;7}

  3. console.log(publish(eventName));

    10const action: Action = "created";11const eventName: EventName = `${entity}:${action}`;1213console.log(publish(eventNameuser:created));
    outputpublish user:created

  1. entity ← order, action ← created, eventName ← order:created

    6    return `publish ${eventName}`;7}89const entity→ order: Entity = "order";10const action→ created: Action = "created";11const eventName→ order:created: EventName = `${entityorder}:${actioncreated}`;1213console.log(publish(eventNameorder:created));

  2. function publish(eventName: EventName): string

    2type Action = "created" | "updated";3type EventName = `${Entity}:${Action}`;45function publish(eventNameorder:created: EventName): string {6    return `publish ${eventNameorder:created}`;7}

  3. console.log(publish(eventName));

    10const action: Action = "created";11const eventName: EventName = `${entity}:${action}`;1213console.log(publish(eventNameorder:created));
    outputpublish order:created