Create polyfill for JavaScript (#5838)

* Create polyfill for JavaScript

* Update polyfill.md

* Delete content/javascript/concepts/methods directory

* Create polyfill

* Create polyfill.md

* Delete content/javascript/polyfill

* Delete content/javascript/polyfill.md

* Add polyfill file

* Add methods back

---------

Author: DanielAsare-ux

content/javascript/concepts/polyfill/polyfill.md

@@ -0,0 +1,76 @@
+---
+Title: 'Polyfill'
+Description: 'Adds modern functionality to older browsers lacking native support, ensuring compatibility and consistent behavior.'
+Subjects:
+  - 'Computer Science'
+  - 'Developer Tools'
+  - 'Web Development'
+Tags:
+  - 'Developer Tools'
+  - 'Browsers'
+  - 'Browser Compatibility'
+  - 'Functions'
+  - 'Programming'
+CatalogContent:
+  - 'introduction-to-javascript'
+  - 'paths/front-end-engineer-career-path'
+---
+
+A **polyfill** is a small piece of JavaScript code that enables modern functionality in browsers that lack native support for specific features. Polyfills act as a fallback, ensuring compatibility and consistent behavior across different environments.
+
+For example, if a browser doesn't support the `Array.prototype.includes` method, a polyfill can add the missing feature, allowing developers to write code that uses modern syntax and APIs without compatibility concerns.
+
+Polyfills are especially useful for:
+
+- Supporting legacy browsers like Internet Explorer.
+- Implementing modern JavaScript methods or APIs (e.g., Promises, Fetch API).
+- Ensuring a consistent user experience across different platforms.
+
+## Syntax
+
+Here's the syntax for a polyfill that typically checks if a method or feature is already available, and if not, it defines the missing functionality:
+
+```pseudo
+if (!Feature.prototype.method) {
+  // Define the polyfill for the missing method
+  Feature.prototype.method = function() {
+    // Polyfill implementation
+  };
+}
+```
+
+- `feature`: The object, class, or prototype (like `String`, `Array`, `Object`, or custom objects) that is missing the method or functionality. The polyfill ensures this feature becomes available on it.
+- `method`: The specific method (e.g., `includes`, `assign`, etc.) that is missing and needs to be added by the polyfill.
+- `if (!Feature.prototype.method)`: Condition that checks if the method is missing in the current environment and only applies the polyfill if it's absent.
+
+## Example
+
+Here’s an example that demonstrates how a polyfill works by adding the missing `includes` method to the `Array` prototype:
+
+```js
+if (!Array.prototype.includes) {
+  // Polyfill for the 'includes' method
+  Array.prototype.includes = function (element) {
+    for (let i = 0; i < this.length; i++) {
+      if (this[i] === element) {
+        return true;
+      }
+    }
+    return false;
+  };
+}
+
+// Example usage of the polyfill
+const arr = [1, 2, 3, 4];
+console.log(arr.includes(3));
+console.log(arr.includes(5));
+```
+
+The output will be as follows:
+
+```shell
+true
+false
+```
+
+Here the code first checks if the `Array.prototype.includes` method exists. If it's missing, the polyfill defines it. The polyfill works by iterating through the array and returning `true` if the specified element is found, or `false` if it's not.