Node.js is required for the installation of some JupyterLab extensions because many extensions are built using JavaScript and use Node.js as a runtime environment. Node.js is an open-source, cross-platform JavaScript runtime environment that allows developers to run JavaScript code outside of a web browser.When installing a JupyterLab extension that requires Node.js, you first need to make sure that Node.js is installed on your system. You can check if Node.js is installed by opening a terminal window and running the command node -v. If Node.js is not installed, you can download and install it from the official Node.js website.Once Node.js is installed, you can install JupyterLab extensions that require it using the npm command, which is the package manager for Node.js.For example, to install the jupyterlab-toc extension, which requires Node.js, you would run the following command in a terminal window:jupyter labextension install @jupyterlab/toc``jupyter labextension install @jupyterlab/toc