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What is Polyfills?

Web development is a rapidly evolving field, with new features and technologies constantly being introduced. However, not all browsers keep up with these changes at the same pace, which can lead to inconsistencies in how a website behaves across different browsers1. This is where polyfills come into play.

What is a Polyfill?​

A polyfill is a piece of code, usually JavaScript, that provides modern functionality on older browsers that do not natively support it.

For example, if a new JavaScript method is introduced that isn’t supported in an older browser, a polyfill could be used to provide this functionality so that the website works as expected.

Why Use a Polyfill?​

The main reason to use a polyfill is to ensure cross-browser compatibility.

By using a polyfill, you can write your code using the latest web technologies without worrying about whether it will work on older browsers.

This allows you to provide a consistent user experience, regardless of the browser that the user is using.

How to Use a Polyfill?​

Polyfills are typically used in conjunction with a transpiler like Babel. A transpiler converts modern JavaScript code into a version that can be understood by older browsers. The polyfill then adds the missing functionality to these older browsers.

Here’s a simple example of a polyfill for the Array.prototype.includes method, which is not supported in Internet Explorer:

if (!Array.prototype.includes) {
  Array.prototype.includes = function(element) {
    return this.indexOf(element) !== -1;
  };
}

In this example, we first check if the includes method exists on the Array.prototype.

If it doesn’t, we define it. The includes method checks if an array contains a certain element, which we mimic using the indexOf method.

Limitations of Polyfills​

While polyfills are incredibly useful, they do have some limitations.

They add extra weight to your web application, as they require loading additional scripts. This can affect performance and loading time.

Also, there’s always a risk of subtle differences in behavior and performance compared to the native implementation.

Conclusion​

In conclusion, polyfills are a powerful tool that can help bridge the gap between modern web technologies and older browsers. They allow you to use the latest and greatest features in your code, without having to worry about leaving users of older browsers behind.