Last active
July 23, 2024 17:22
-
-
Save nicolashery/da9c101891ca0c9f9ceb to your computer and use it in GitHub Desktop.
Sketchpad: Event-driven design in TypeScript
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
// Playing around with TypeScript | |
// Inspiration: https://github.com/abdullin/omni | |
// core.event | |
interface DomainEventType { | |
name: string; | |
} | |
interface DomainEvent { | |
_type: DomainEventType; | |
} | |
// lang.ids | |
type EventId = string; | |
type TaskId = string; | |
// lang.events | |
var TaskAdded: DomainEventType = {name: 'TaskAdded'}; | |
interface TaskAddedAttributes { | |
eventId: EventId; | |
taskId: TaskId; | |
name: string; | |
} | |
interface TaskAddedEvent extends DomainEvent, TaskAddedAttributes {} | |
function newTaskAdded(attr: TaskAddedAttributes): TaskAddedEvent { | |
return objectAssign(attr, {_type: TaskAdded}); | |
} | |
var TaskRemoved: DomainEventType = {name: 'TaskRemoved'}; | |
interface TaskRemovedAttributes { | |
eventId: EventId; | |
taskId: TaskId; | |
} | |
interface TaskRemovedEvent extends DomainEvent, TaskRemovedAttributes {} | |
function newTaskRemoved(attr: TaskRemovedAttributes): TaskRemovedEvent { | |
return objectAssign(attr, {_type: TaskRemoved}); | |
} | |
// views.store | |
interface TaskItem { | |
taskId: TaskId; | |
name: string; | |
inbox: boolean; | |
} | |
interface Store { | |
[index: string]: TaskItem; | |
} | |
function addTask(s: Store, id: TaskId, name: string): Store { | |
s[id] = { | |
taskId: id, | |
name: name, | |
inbox: false | |
}; | |
return s; | |
} | |
function removeTask(s: Store, id: TaskId): Store { | |
delete s[id]; | |
return s; | |
} | |
// views.denormalizer | |
function handleEvent(s: Store, e: any): Store { | |
// Would've liked to use `e: DomainEvent` in func signature but can't... | |
switch (e._type) { | |
case TaskAdded: | |
s = addTask(s, e.taskId, e.name); | |
break; | |
case TaskRemoved: | |
s = removeTask(s, e.taskId); | |
break; | |
} | |
return s; | |
} | |
// playground | |
var s: Store = {}; | |
var e1: TaskAddedEvent = newTaskAdded({ | |
eventId: '12', | |
taskId: '45', | |
name: 'Clean dishes' | |
}); | |
var e2: TaskRemovedEvent = newTaskRemoved({ | |
eventId: '34', | |
taskId: '45' | |
}); | |
console.log(JSON.stringify(s)); | |
s = handleEvent(s, e1); | |
console.log(JSON.stringify(s)); | |
s = handleEvent(s, e2); | |
console.log(JSON.stringify(s)); | |
// lib | |
function objectAssign (target, source) { | |
var from; | |
var keys; | |
var to = Object(target); | |
for (var s = 1; s < arguments.length; s++) { | |
from = arguments[s]; | |
keys = Object.keys(Object(from)); | |
for (var i = 0; i < keys.length; i++) { | |
to[keys[i]] = from[keys[i]]; | |
} | |
} | |
return to; | |
}; |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment