init

Author: mrkmx

Diff for: .tool-versions

@@ -0,0 +1 @@
+nodejs 21.6.1

Diff for: event-emitter.js

@@ -0,0 +1,75 @@
+class EventEmitter {
+    constructor() {
+        this.listeners = new Map()
+    }
+    on(event, cb, once = false) {
+        if (!this.listeners.has(event)) {
+            this.listeners.set(
+                event,
+                {
+                    callbacks: new Set, // use Set to register callback once
+                    once,
+                }
+            )
+        }
+        this.listeners.get(event).callbacks.add(cb)
+        
+        return this // support chaining
+    }
+    once(event, cb) {
+        const once = true
+        this.on(event, cb, once)
+    }
+    off(event, cb) {
+        if (!this.listeners.has(event)) return
+
+        this.listeners.get(event).callbacks.delete(cb)
+        
+        return this
+    }
+    // TODO: check use cases for args and chaining, it looks dumb
+    emit(event, ...args) {
+        // check unregistered event
+        if (!this.listeners.has(event)) return
+        
+        const {callbacks, once} = this.listeners.get(event)
+        for (const cb of callbacks) {
+            // support callback args 
+            cb(...args)
+        }
+
+        if (once) {
+            this.listeners.delete(event)
+        }
+
+        return this
+    }
+}
+
+const emitter = new EventEmitter()
+
+function one () {console.log('one')}
+function two () {console.log('two')}
+function three () {console.log('three')}
+function doubleAndPrint (num, str) {console.log(num * 2, str)}
+
+emitter.on('run', one)
+emitter.on('run', two)
+emitter.on('run', two)
+emitter.on('run', three)
+emitter.on('run', doubleAndPrint)
+emitter.off('run', three)
+
+emitter.on('chain', three)
+       .on('chain', two)
+       .on('chain', one)
+       .on('other', doubleAndPrint)
+       .emit('other', 5 ,7)
+
+emitter.emit('run', 5, 7)
+emitter.emit('chain')
+
+emitter.once('onlyOnce', two)
+emitter.emit('onlyOnce')
+emitter.emit('onlyOnce')
+emitter.emit('onlyOnce')