Node.js Local Modules: Create and Use Custom Modules for Better Code Organization

Learn how to create and use local modules in Node.js to enhance code organization and reusability. This guide covers creating a custom module, defining a log object, and exporting it for use in your project.

Node.js Local Module

Local modules are created within your project for specific functionalities. They enhance code organization and reusability and are not published to the public registry (unlike npm packages).

Creating a Local Module (Log.js)

1. File Creation: Create a file named Log.js.
2. Module Object: Define an object (log) with functions for logging (info, warning, error).
3. Exporting the Module: Use module.exports = log to expose the log object as the module.

Log.js

        
var log = {
    info: function (info) { 
        console.log('Info: ' + info);
    },
    warning: function (warning) { 
        console.log('Warning: ' + warning);
    },
    error: function (error) { 
        console.log('Error: ' + error);
    }
};

module.exports = log;
        
    

Using a Local Module (app.js)

1. Require Statement: Use var myLogModule = require('./Log.js') to import the module from ./Log.js (current directory).
2. Using the Module: Access the exposed object's methods using dot notation (e.g., myLogModule.info('Node.js started')).

app.js

        
var myLogModule = require('./Log.js');

myLogModule.info('Node.js started');
        
    

Key Points

• module.exports is a special object for exporting functionality from a module.
• The require function is used to import modules into your application.
• The path in require specifies the location of the module file relative to the current file.

Additional Considerations

• You can export functions, variables, or even classes using module.exports.
• Local modules can have dependencies on other local modules or core Node.js modules.
• For complex projects, consider structuring modules in folders for better organization.

By effectively utilizing local modules, you can create well-structured, maintainable, and reusable Node.js applications.

Running the Example

Run the above example using the command prompt (in Windows) as shown below:

        
C:\> node app.js
Info: Node.js started
        
    

Thus, you can create a local module using module.exports and use it in your application.