If you dont have Node.js already installed on your computer, then you need to install it first. To verify whether Node.js is already installed on your computer please run this command.
If this returns you a version number then that means node.js is installed on your computer. e.g) In my case it is returning "v10.16.0" If you get any error, then we need to install Node.js.
Installing Node.js is very easy. Visit Node.js website You will see a download option for your Windows or MacOS. Download the one where it says "Recommended for Most Users" and simply run the installer. When the installation is finished you should be able to run this command.