Event Emitter

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Simple Event Emitter or PubSub pattern

class Event {
constructor() {
this.events = {}
}
subscribe(event, handler) {
this.events[event] = this.events[event] || []
this.events[event].push(handler)
return () => this.unSubscribe(event, handler)
}
unSubscribe(event, handler) {
let handlers = this.events[event]
if (handlers && Array.isArray(handlers)) {
for (let i = 0; i < handlers.length; i++) {
if (handlers[i] === handler) {
handlers.splice(i, 1)
break
}
}
}
}
emit(event, ...args) {
;(this.events[event] || []).forEach((handler) => {
handler(...args)
})
}
}

Usage

// Create a global instance in your app
let globalEvent = new Event()
let handler1 = (data) => console.log(`handler1(): FOO event emiited with data: ${data}`)
let handler2 = (data) => console.log(`handler2(): FOO event emiited with data: ${data}`)
// Subscribe to event
globalEvent.subscribe("FOO", handler1)
globalEvent.subscribe("FOO", handler2)
// Emit event when needed
globalEvent.emit("FOO", "foo")
// Expected:
// handler1(): FOO event emiited with data: foo
// handler2(): FOO event emiited with data: foo
// Unsubscribe event
globalEvent.unSubscribe("FOO", handler2)
// Then
globalEvent.emit("FOO", "bar")
// Expected:
// handler1(): FOO event emiited with data: bar