add: fixing setting up a callback

Author: supercodestart

README.md

@@ -3,6 +3,7 @@
 - [Filling all the missed angle brackets](filling-all-the-missed-angle-brackets)
 - [Finding all the anagrams](finding-all-the-anagrams)
 - [Finding the maximum depth of a binary tree](finding-the-maximum-depth-of-a-binary-tree)
+- [Fixing setting up a callback](fixing-setting-up-a-callback)
 - [Getting the distinct transactions](getting-the-distinct-transactions)
 - [Replacing with the cipher letters](replacing-with-the-cipher-letters)
 - [Validating a maze path](validating-a-maze-path)

fixing-setting-up-a-callback/README.md

@@ -0,0 +1,70 @@
+# Fixing setting up a callback
+
+The below code has an error. Fix it.
+
+```javascript
+const solution = (messages) => {
+  class Emitter {
+    constructor(messages = []) {
+      this.messages = messages;
+      this.event = () => {};
+    }
+
+    setEvent(fn) {
+      this.event = fn;
+    }
+
+    trigger() {
+      this.messages.forEach((message) =>
+        this.event(message),
+      );
+    }
+  }
+
+  class Receiver {
+    constructor() {
+      this.messages = [];
+    }
+
+    ping(message) {
+      this.messages.push(message);
+    }
+  }
+
+  const myEmitter = new Emitter(messages);
+  const myReceiver = new Receiver();
+
+  myEmitter.setEvent(myReceiver.ping);
+  myEmitter.trigger();
+
+  return myReceiver.messages;
+};
+```
+
+Input
+
+```console
+[
+  'Hello~',
+  'Can you hear me?',
+  'Nice to meet you.',
+  'This is a test message.',
+]
+```
+
+Output
+
+```console
+[
+  'Hello~',
+  'Can you hear me?',
+  'Nice to meet you.',
+  'This is a test message.',
+]
+```
+
+## Execute
+
+```bash
+node solution.js
+```

fixing-setting-up-a-callback/solution.js

@@ -0,0 +1,47 @@
+const solution = (messages) => {
+  class Emitter {
+    constructor(messages = []) {
+      this.messages = messages;
+      this.event = () => {};
+    }
+
+    setEvent(fn) {
+      this.event = fn;
+    }
+
+    trigger() {
+      this.messages.forEach((message) =>
+        this.event(message),
+      );
+    }
+  }
+
+  class Receiver {
+    constructor() {
+      this.messages = [];
+    }
+
+    ping(message) {
+      this.messages.push(message);
+    }
+  }
+
+  const myEmitter = new Emitter(messages);
+  const myReceiver = new Receiver();
+
+  myEmitter.setEvent(myReceiver.ping.bind(myReceiver));
+  myEmitter.trigger();
+
+  return myReceiver.messages;
+};
+
+(() => {
+  console.log(
+    solution([
+      'Hello~',
+      'Can you hear me?',
+      'Nice to meet you.',
+      'This is a test message.',
+    ]),
+  );
+})();