Polyfill

A polyfill is a piece of code (usually JavaScript) that provides the functionality of newer browser features to older browsers that do not natively support those features. Polyfills are used to ensure that a website or web application behaves consistently across different browsers, regardless of their level of support for modern web standards.

When a browser encounters a feature that it does not support, it will ignore that feature or throw an error. Polyfills detect these unsupported features and provide alternative implementations that mimic the behavior of the newer features. This allows developers to use the latest web technologies while still ensuring compatibility with older browsers.

Example:

// Example of a polyfill for the Array.prototype.includes method
if (!Array.prototype.includes) {
    Array.prototype.includes = function(searchElement, fromIndex) {
        // Implementation of the includes method for older browsers
    };
}