partial fix: what-are-callback-functions-and-how-are-they-used

Author: tahachm

questions/what-are-callback-functions-and-how-are-they-used/en-US.mdx

@@ -6,12 +6,11 @@ title: What are callback functions and how are they used?
 
 A callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action. They are commonly used for asynchronous operations like handling events, making API calls, or reading files. For example:
 
-```js
+```js live
 function fetchData(callback) {
-  setTimeout(() => {
-    const data = { name: 'John Doe' };
-    callback(data);
-  }, 1000);
+  // assume an asynchronous operation to fetch data
+  const data = { name: 'John Doe' };
+  callback(data);
 }
 
 function handleData(data) {
@@ -33,7 +32,7 @@ A callback function is a function that is passed as an argument to another funct
 
 Synchronous callbacks are executed immediately within the function they are passed to. They are often used for tasks that need to be completed before moving on to the next line of code.
 
-```js
+```js live
 function greet(name, callback) {
   console.log('Hello ' + name);
   callback();
@@ -44,6 +43,9 @@ function sayGoodbye() {
 }
 
 greet('Alice', sayGoodbye);
+// Output:
+// Hello Alice
+// Goodbye!
 ```
 
 ### Asynchronous callbacks
@@ -105,7 +107,7 @@ function sayHello() {
   console.log('Hello, world!');
 }
 
-setTimeout(sayHello, 2000);
+setTimeout(sayHello, 2000); // After 2 seconds elapse, sayHello callback is called
 ```
 
 ## Further reading