Overview
A well-liked JavaScript library for creating user interfaces is called React. Developers can easily and effectively manage state with React and build reusable components. But when several browsers and gadgets don't support the same functionalities, there may be compatibility problems, just as with any JavaScript programme. Polyfills are useful in this situation.
Describe Polyfills
Code fragments called polyfills
offer functionality for features that might not be supported by all browsers
or operating systems
. They enable programmers to guarantee that their code operates as intended across all platforms, regardless of any restrictions on feature support.
If you want to know more about polyfills
go to this link
Why Do React Users Use Polyfills?
Making sure a React application is compatible with as many browsers as feasible is crucial when developing one. This is crucial for developing online applications that consumers may access on a variety of platforms and devices.
Many of the contemporary JavaScript features used by React might not be supported by earlier browsers like Internet Explorer. By providing fallback code for features that aren't supported, polyfills can aid in ensuring that these features function properly across all browsers.
Examples of Polyfills in React
Here are some more examples of popular JavaScript features used in React that may require polyfills:
-
Promise:
- Promises are used in React for asynchronous operations. However, they are not supported in older versions of Internet Explorer.
- To use Promises in all browsers, you can add a polyfill for them, such as the es6-promise package.
- This package provides a Promise implementation that works in older browsers, allowing you to use Promises in your React application without any compatibility issues.
-
Object.assign():
- This method is used in React for merging objects. However, it is not supported in older versions of Internet Explorer.
- To use Object.assign() in all browsers, you can add a polyfill for it, such as the object-assign package.
- This package provides an Object.assign() implementation that works in older browsers, allowing you to use this method in your React application without any compatibility issues.
-
Fetch API:
- The
Fetch API
is used in React for making HTTP requests. However, it is not supported in older versions ofInternet Explorer
. - To use the Fetch API in all browsers, you can add a polyfill for it, such as the
whatwg-fetch
package. - This package provides a Fetch API implementation that works in
older browsers
, allowing you to use this feature in your React application without any compatibility issues.
- The
-
Symbol:
-
Symbols
are used in React for creating unique identifiers. However, they are not supported in some older browsers. - To use
Symbols
in your React application, you can add a polyfill for them, such as thecore-js
package. - This package provides a
Symbol
implementation that works inolder browsers
, allowing you to use this feature in your React application without any compatibility issues.
-
-
String.startsWith():
-
startsWith
method determines whether a string begins with the characters of a specified string, returning true or false as appropriate. However, it is not supported in older versions ofInternet Explorer
. - To use
startsWith
in your React application, you can add a polyfill for them, such as the core-js package. - This package provides a
String.prototype.startsWith()
implementation that works inolder browsers
, allowing you to use this method in your React application without any compatibility issues.
-
-
Array.includes():
- The
Array.includes()
method in React is used to determine whether an array contains a specific value. Older versions ofInternet Explorer
do not, however, support it. - You can include a
polyfill
forArray.includes()
, such as thearray-includes
package, to make it work in all browsers. - You can use the
Array.includes()
method in yourReact
application without encountering any compatibility problems thanks to this package's implementation, which supports older browsers.
- The
-
Object.entries():
- This method is used in React for getting an object's key-value pairs as an array. However, it is not supported in older versions of
Internet Explorer
. - To use
Object.entries()
in all browsers, you can add a polyfill for it, such as theobject.entries
package. - This package provides an
Object.entries()
implementation that works inolder browsers
, allowing you to use this method in your React application without any compatibility issues.
- This method is used in React for getting an object's key-value pairs as an array. However, it is not supported in older versions of
Writing polyfills from scratch
Here is an example of how to write a polyfill from scratch for the startsWith
method in React:
In this example, we first determine whether the String prototype's startsWith
method already exists. If it doesn't already exist, we define it as a function that accepts search
and pos
as parameters.
The substr
method is then used by the function to extract a section of the string beginning with the pos
argument, or 0 in the absence of pos
or if pos
is less than 0. The search parameter is then compared to this substring using rigorous equality (===), and a boolean
result is returned.
The startsWith
method may be made to function as intended in all browsers, even those that don't support it natively, by specifying this polyfill.
Here's another example of how to create a polyfill for the array includes
method:
This polyfill verifies whether the Array.prototype
object already defines the includes
method. It generates a new function that accepts an elementToBeSearched
parameter if it is not defined.
The function then used a for loop to iterate through the array, inspecting each element to see if it matches the elementToBeSearched
parameter. It returns true
if it discovers a match. The function returns false
if it cannot locate a match.
If you want to write more polyfill
from scratch go to this link
NOTE:
It's important to note that writing a polyfill
from scratch
can be challenging, especially for complex features
. In addition, it's important to thoroughly test the polyfill in various browsers
and environments
to ensure it behaves correctly and doesn't cause any unexpected issues.
How to Add Polyfills in React
You can use a library containing a collection of polyfills that will perform the same function for you instead of manually checking for the existence of a feature and adding a polyfill.
Use pre-existing polyfills or packages whenever possible; only create your own if absolutely essential and if you have the necessary knowledge and experience.
--
Example 1:
Adding polyfills in React is a simple process. Here's how you can add a polyfill for startsWith
:
- Install the core-js package as a dependency in your project:
npm install core-js
- Import the startsWith polyfill at the top of your JavaScript file:
import 'core-js/actual/string/starts-with';
- Now you can use the startsWith method in your React components, like this:
const testString = 'Hi all JavaScript Developer out there!';
const startsWithHi = testString.startsWith('Hi');
console.log(startsWithHi); // true
We can make sure that the startsWith
method functions as intended in all browsers, even those that don't support it natively, by importing the startsWith
polyfill from core-js
.
Example 2:
Let's take another example of how to add a polyfill for Array.includes():
- Install the array-includes package using npm:
npm install array-includes
- Import the package in your JavaScript code:
import 'array-includes/auto';
This will automatically add the polyfill
for Array.includes()
to your React application.
Example 3:
Here is another example of how to use a polyfill for Promise
in a React project:
- Install the
es6-promise
package usingnpm
:
npm install es6-promise
- Import the package in your JavaScript code:
import 'es6-promise/auto';
This will automatically add the polyfill for Promise to your React application.
Conclusion
Polyfills are an essential tool for ensuring browser compatibility in React applications. By providing fallback code for unsupported features, polyfills help developers create web applications that work seamlessly across all browsers and platforms.
If you're developing a React application, it's important to consider the use of polyfills to ensure maximum compatibility. With the right polyfills in place, you can be confident that your application will work as intended, regardless of any feature support limitations in the browser or environment.
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Top comments (1)
great article, thank you. Do we need to add the import to every react js file that uses the function or just to index.js? I'm having serious problems with object.entries on iOS 10. I keep hitting the error Unhandled promise rejection TypeError: t.entries is not a function. (In 't.entries()', 't.entries' is undefined). I have imported/installed various object.entries polyfills and also the es6-promise but it hasn't resolved the issue.