javascript - How to use the 'main' parameter in package.json?

Question

I have done quite some search already. However, still having doubts about the 'main' parameter in the package.json of a Node project.

1. How would filling in this field help? Asking in another way, can I start the module in a different style if this field presents?
2. Can I have more than one script filled into the main parameter? If yes, would they be started as two threads? If no, how can I start two scripts in a module and having them run in parallel?

I know that the second question is quite weird. It is because I have hosted a Node.js application on OpenShift but the application consists of two main components. One being a REST API and one being a notification delivering service.

I am afraid that the notification delivering process would block the REST API if they were implemented as a single thread. However, they have to connect to the same MongoDB cartridge. Moreover, I would like to save one gear if both the components could be serving in the same gear if possible.

Any suggestions are welcome.

Answer 1

From the npm documentation:

The main field is a module ID that is the primary entry point to your program. That is, if your package is named foo, and a user installs it, and then does require("foo"), then your main module's exports object will be returned.

This should be a module ID relative to the root of your package folder.

For most modules, it makes the most sense to have a main script and often not much else.

To put it short:

1. You only need a main parameter in your package.json if the entry point to your package differs from index.js in its root folder. For example, people often put the entry point to lib/index.js or lib/<packagename>.js, in this case the corresponding script must be described as main in package.json.
2. You can't have two scripts as main, simply because the entry point require('yourpackagename') must be defined unambiguously.