-
-
Save adrianvlupu/aa4ee93f6e60018d3365f9a668548d3e to your computer and use it in GitHub Desktop.
A straight forward EventEmitter implemented in Javascript using ES6
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
let isFunction = function(obj) { | |
return typeof obj == 'function' || false; | |
}; | |
class EventEmitter { | |
constructor() { | |
this.listeners = new Map(); | |
} | |
addListener(label, callback) { | |
this.listeners.has(label) || this.listeners.set(label, []); | |
this.listeners.get(label).push(callback); | |
} | |
removeListener(label, callback) { | |
let listeners = this.listeners.get(label), | |
index; | |
if (listeners && listeners.length) { | |
index = listeners.reduce((i, listener, index) => { | |
return (isFunction(listener) && listener === callback) ? | |
i = index : | |
i; | |
}, -1); | |
if (index > -1) { | |
listeners.splice(index, 1); | |
this.listeners.set(label, listeners); | |
return true; | |
} | |
} | |
return false; | |
} | |
emit(label, ...args) { | |
let listeners = this.listeners.get(label); | |
if (listeners && listeners.length) { | |
listeners.forEach((listener) => { | |
listener(...args); | |
}); | |
return true; | |
} | |
return false; | |
} | |
} | |
class Observer { | |
constructor(id, subject) { | |
this.id = id; | |
this.subject = subject; | |
this.subject.addListener("change", (data) => this.onChange(data)); | |
} | |
onChange(data) { | |
console.log(`(${this.id}) notified of change:`, data); | |
} | |
} | |
let observable = new EventEmitter(); | |
let [observer1, observer2] = [ | |
new Observer(1, observable), | |
new Observer(2, observable) | |
]; | |
observable.emit("change", { a: 1 }); |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment