Node.js Rewrite Module Functions

Rewriting the functions of Node.js modules

Alternative functions for Node.js modules – in someIn cases where you want to improve the functionality of an existing module by rewriting it. In this Node.js tutorial, we will learn how to rewrite the functions of Node.js modules.

To rewrite the existing functions of a Node.js module, please follow the following step-by-step guide:

Introduce the module

The first step to override a function in the module is to include the module itself using the require function.

var newMod = require('<module_name>');

We have retrieved the module into the variable.

Remove the function from the module variable

Use the following syntax to remove the function from the variable in the module newMod.

　　delete newMod['<function_name>'];

Remember that the changes made are only to the module variable newMod, and not to the original module itself.

Add a function with the same name to the module variable

In the module newMod, use the following syntax to add a function with the same name as the one deleted in the previous step.

newMod.<function_name> = function(function_parameters) {
　//　function body
};

Reexport the module

You must reexport the module to make the overridden functionality take effect.

module.exports = newMod;

Now, you can use the variable newMod for the module to call the function, and then execute the overridden functionality.

Example: Overriding Functionality of Node.js Modules

In this example, we will override the readFile() function of the Node fs module.

The first step to override a function in a module is to use the require function to include the module itself.

//　Include the module that you want to override its functionality
var fs = require('fs');　
　
//　Delete the functionality you want to override
delete fs['readFile'];　
　
//　Add a new function with the same name as the deleted function
fs.readFile = function(str){　
　　　　console.log("The functionality has been overridden.");　
　　　　console.log(str);　
　}　
　
//　Reexport the module to make the changes take effect
module.exports = fs
　
//　You can use the new overridden functionality
fs.readFile("sample.txt");

Output Result

~/workspace/nodejs$ node node-js-overriding-function-in-module.js 
Message from newly added function to the module
sample.txt

Conclusion:

In this tutorial–Rewriting Node.js Module FunctionalityWe have learned to use the example Node.js program to cover the functionality of Node.js modules.