How does script tag resolves path to node_modules?

Question

I was reading this Node.js In Action and there's this index.html which references socket.io.js from node_modules folder (I believe).

How does the following script tag resolves the path to the socket.io.js when the node_modules folder is one directory up from where the index.html resides?

The script tag:

<script src="/socket.io/socket.io.js" type="text/javascript"></script>

Answer 1

• Socket.io reads the content of the socket.io-client/socket.io.js file into a variable.

• Socket.io has access to your app's http server, it then listens to requests that would match the URL of something like '/socket.io/socket.io.js' and responds with the contents of that variable above

You can see this in the socket.io source code :

• Reading the .js source code
• Serving the .js file

Answer 2

When you include a module in your file, node first looks for the module in node_modules folder in current directory. If it does not find it there then it moves to parent directory and looks for the module in node_modules present in that directory, and it keeps moving up until it finds the required module.