wip: add more questions

src/data/question-groups/javascript/content/iife.md

@@ -0,0 +1,18 @@
+The IIFE (Immediately Invoked Function Expression) is a JavaScript function that runs as soon as it is defined.
+
+```js
+(function () {
+  console.log('Hello Roadmap!');
+})();
+```
+
+The IIFE is frequently used to create a new scope to avoid variable hoisting from within blocks.
+
+```js
+(function () {
+  var roadmap = 'JavaScript';
+  console.log(roadmap);
+})();
+
+console.log(roadmap); // ReferenceError: name is not defined
+```

src/data/question-groups/javascript/content/inheritance.md

@@ -0,0 +1,38 @@
+Inheritance is a way to create a new `Class` from an existing `Class`. The new `Class` inherits all the properties and methods from the existing `Class`. The new `Class` is called the child `Class`, and the existing `Class` is called the parent `Class`.
+
+## Example
+
+```js
+class Roadmap {
+  constructor(name, description, slug) {
+    this.name = name;
+    this.description = description;
+    this.slug = slug;
+  }
+
+  getRoadmapUrl() {
+    console.log(`https://roadmap.sh/${this.slug}`);
+  }
+}
+
+class JavaScript extends Roadmap {
+  constructor(name, description, slug) {
+    super(name, description, slug);
+  }
+
+  greet() {
+    console.log(`${this.name} - ${this.description}`);
+  }
+}
+
+const js = new JavaScript(
+  'JavaScript Roadmap',
+  'Learn JavaScript',
+  'javascript'
+);
+
+js.getRoadmapUrl(); // https://roadmap.sh/javascript
+js.greet(); // JavaScript Roadmap - Learn JavaScript
+```
+
+In the above example, the `JavaScript` class inherits the `getRoadmapUrl()` method from the `Roadmap` class. This is because the `JavaScript` class extends the `Roadmap` class using the `extends` keyword. In the `JavaScript` class, the `getRoadmapUrl()` method is not found, so JavaScript looks up the prototype chain and finds the `getRoadmapUrl()` method in the `Roadmap` class.

src/data/question-groups/javascript/javascript.md

@@ -103,4 +103,14 @@ questions:
     topics:
       - 'OOP'
       - 'Advanced'
+  - question: What is IIFE in JavaScript?
+    answer: iife.md
+    topics:
+      - 'Core'
+      - 'Advanced'
+  - question: What is Inheritance in JavaScript?
+    answer: inheritance.md
+    topics:
+      - 'OOP'
+      - 'Advanced'
 ---