Add createEventHub

snippets/createEventHub.md

@@ -0,0 +1,36 @@
+### createEventHub
+
+Creates a pubsub event hub with `emit`, `on`, and `off` methods.
+
+For `emit`, resolve the array of handlers based on the `event` argument and then run
+each one by passing in the data as an argument.
+
+For `on`, create an array for the event if it does not yet exist, then push the handler
+into the array.
+
+For `off`, find the index of the handler in the event array and remove it.
+
+```js
+const createEventHub = () => ({
+  hub: {},
+  emit(event, data) {
+    this.hub[event].forEach(handler => handler(data));
+  },
+  on(event, handler) {
+    if (!this.hub[event]) this.hub[event] = [];
+    this.hub[event].push(handler);
+  },
+  off(event, handler) {
+    const i = this.hub[event].findIndex(h => h === handler);
+    if (i) this.hub[event].splice(i, 1);
+  }
+});
+```
+
+```js
+const hub = createEventHub();
+const fn = data => console.log(data);
+hub.on('message', fn); // subscribe a handler to listen for 'message' events
+hub.emit('message', 'hello!'); // console logs 'hello!'
+hub.off('message', fn); // unsubscribe our handler from 'message'
+```