Installing React

Let’s try it by running yarn add react@15.6.1 from within your project folder.

Once the installation is complete, you should see React added to our package.json under dependencies. You'll also see that yarn generated a node_modules folder and a yarn.lock file.

The node_modules folder is where all our packages will live. If you open it up, you can see that there are several folders already. We've not only installed React, but everything that React depends on--dependencies on dependencies.

As you might imagine, the node_modules folder can get quite hefty. So, we don't check it into source control. When a new developer joins the team and downloads the project files, they can then install the dependencies independently, based on the package.json; this saves time and space.

However, we need to ensure that they get the same packages as everyone else, and the same version; this is where the yarn.lock file comes in.

The previously mentioned setup ensures that we are ready to safely use third-party libraries. We have the package.json, yarn.lock, and node_modules folders in our project. Before we continue, let's ensure that adding React worked.