Referenceerror: textencoder is not defined jest

The “ReferenceError: TextEncoder is not defined” error in Jest occurs when the TextEncoder object is not available in the testing environment. The TextEncoder is a built-in JavaScript object used for encoding strings to UTF-8.

This error commonly occurs when using Jest for testing JavaScript code that relies on features not provided by the testing environment, such as the TextEncoder object which is typically available in browsers.

To resolve this error, you can use a polyfill to provide the TextEncoder object in the Jest testing environment. A polyfill is a piece of code that replicates the behavior of a missing feature in an environment that lacks support for it. One such polyfill for the TextEncoder is the “text-encoding” npm package.

First, install the “text-encoding” npm package by running the following command in your project directory:

    npm install --save text-encoding
  

Then, import the TextEncoder polyfill at the beginning of your test file(s) using the “text-encoding” package:

    import { TextEncoder } from 'text-encoding';
  

By importing the “TextEncoder” object from the “text-encoding” package, you will be able to use it in your Jest tests without encountering the “ReferenceError: TextEncoder is not defined” error.

Here’s an example of how you can use the “TextEncoder” polyfill in a Jest test:

    import { TextEncoder } from 'text-encoding';

    test('Encode string to UTF-8', () => {
      const encoder = new TextEncoder();
      const encodedText = encoder.encode('Hello, world!');
      
      expect(encodedText).toBeInstanceOf(Uint8Array);
      expect(encodedText).toHaveLength(13);
    });
  

In the above example, the “TextEncoder” polyfill is used to create an encoder object that encodes the “Hello, world!” string to UTF-8. The resulting encoded text is then asserted to be an instance of Uint8Array and have a length of 13 bytes.