# Polyfills In Java-script

What is Polyfills and How implemented Polyfill in JavaScript.

A polyfill is a piece of code (usually JavaScript on the Web) used to provide modern functionality on older browsers that do not natively support it and better understand the Prototype Functionality.

You may be familiar with the phrase polyfill as a developer. In a continuously changing technological landscape where new capabilities are frequently added to programming languages and online platforms, polyfills are an essential component of web development

**Need for Polyfills:**

1. **New features:** Polyfills enable programmers to use cutting-edge functions of a web platform or programming language in older browsers or environments that don't support them.
    
2. **Browser Compatibility:** The latest features of a programming language or web platform may not be supported by all browsers and environments, which can cause compatibility problems for developers. Polyfills aid in ensuring that the code functions consistently on various browsers and gadgets.
    

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739301691016/624cb3eb-3b04-4af4-950a-bc2274f3475a.png align="center")

**Implementing Polyfills in JavaScript :**

Implementing polyfills in JavaScript is simple. In this part, we'll examine a couple of code examples that demonstrate how to use polyfills.

**Step 1:** **Identify the missing feature-**

• Finding the feature that is absent from the browser or environment is the first step in constructing a polyfill.

• This can be accomplished by determining whether the feature is compatible with the browser or by determining whether it is present using feature detection methods like typeof, in, Or window.

**Step 2: Fallback implementation-**

• The next step is to develop the fallback implementation that offers a similar functionality once the missing feature has been located.

**Step 3: Examine the polyfill-**

• It is crucial to properly test the polyfill after implementation to make sure it functions as intended.

• To check that the code provides the same functionality across various contexts and browsers, you can test it.

**Step 4: Implement the polyfill-**

• Implementing the polyfill in your code comes after testing it.

• To achieve this, enclose the code that makes use of the lacking feature in an if statement that verifies the feature's support.

### **Example 1:**

Let’s Imagine we wish to use the **Array.forEach()** methods\*\*;\*\*

Errors: foeEach function does not exits on array variable

RealSignature: Isko Smgha important hai, No return value, function input, value, index.

function call foor every value…

Code Implement…

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739303268830/23300e29-70cc-48c6-853e-311209e47ce3.png align="center")

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739303346820/561d6e13-9576-42ba-8438-af35b6cddf22.png align="center")

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739303383534/fae67672-0780-4df4-92ad-b36064511a73.png align="center")

Dry Run Code Implement….

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739303582373/c7ecf962-65e8-41c8-926d-cef56189fbeb.png align="center")

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739303741230/104f7480-543a-4d54-8580-0c2e84e07198.png align="center")

### **Example 2:**

Let’s Imagine we wish to use the **Array.map()** methods\*\*;\*\*

Errors: Instant create a New array

RealSignature: Isko Smgha important hai, .Map()

Return: NewArray with each element Iterate, userFunction(userFn)

Code Implement…

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739303993254/07ca2a08-d673-4545-aa3a-37e10f63fe20.png align="center")

Dry-Run code implementation…

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739304059065/1104bab7-b9a1-4471-9cd1-147d6c1c009d.png align="center")

### **Example 3:**

Let’s Imagine we wish to use the **Array.filter()** methods\*\*,\*\* Array instance create a shallow copy(“of an object is a copy share the same reference of the source of object“) of given array.

RealSignature: Isko Smgha important hai, .()filter

Return: newArray contain the element, input: userFunction(userFn)

Code Implement…

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739304930603/92556be3-3c0a-472c-99eb-328cdbb1bfc2.png align="center")

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739304369392/9deb0904-a172-4bad-b0a5-d32cc6d0cc00.png align="center")

### **Example 4:**

Let’s Imagine we wish to use the **Array.reduce()** methods\*\*,\*\* Array excute a user supplied “reduce“ callbackFunctio oon each element of the array, inorder, Passing in the return value from the prceding element.

RealSignature: Isko Smgha important hai, .()reduce

Return: excute the each element.

Code Implement…

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739304692847/8fe7ef00-38c1-42f2-81c3-8da3ab4113ab.png align="center")

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739304745749/a9101000-b411-4d16-89fa-63e8abf64566.png align="center")

**Benefits of Polyfills:**

1. B**etter User Experience:** Polyfills allow developers to improve user experience by adding features and capabilities, even in older browsers.
    
2. **Reduced development time:** By enabling developers to use new capabilities without having to write specific code for older browsers, polyfills can save developers a significant amount of effort.
    
3. **Cost-effective:** Polyfills saves money by preventing the need to design specialised solutions for every browser or device by ensuring that your code works on a variety of browsers and mobile devices.
    
4. **Enhanced security:** Using polyfills can also increase security of a different implementation of a feature that might have security flaws in earlier browser versions.
    

**JavaScript Versions:**

It is a programming language used by developers all over the world. It's a lightweight and easy-to-learn language that can run on both the client-side (in your browser) and the server-side (on the server). JavaScript was created in 1995 by Brendan Eich.

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1739555024144/0fc54a5a-a4a6-4272-b6f6-90c5c78712c2.png align="center")

In 1997, JavaScript became a standard, known as ECMAScript. Since then, there have been many versions of ECMAScript, with new features added over the years. Each version after 2016 is named after the year it was released, like ECMAScript 2016, ECMAScript 2017, and so on.