What is node-hook?
The node-hook package allows you to hook into Node.js' require function to modify the behavior of module loading. This can be useful for tasks such as transpiling code on the fly, mocking modules for testing, or adding custom behavior to module loading.
What are node-hook's main functionalities?
Transpile Code on the Fly
This feature allows you to transpile ES6 code to ES5 on the fly using Babel. By hooking into the '.js' extension, you can transform the source code before it is executed.
const hook = require('node-hook');
const babel = require('@babel/core');
hook.hook('.js', (source, filename) => {
const result = babel.transformSync(source, { filename });
return result.code;
});
require('./your-es6-file');
Mocking Modules for Testing
This feature allows you to mock specific modules for testing purposes. By checking the filename, you can return a mocked version of the module.
const hook = require('node-hook');
hook.hook('.js', (source, filename) => {
if (filename.endsWith('some-module.js')) {
return 'module.exports = { mockedFunction: () => "mocked" };';
}
return source;
});
const someModule = require('./some-module');
console.log(someModule.mockedFunction()); // Outputs: mocked
Custom Behavior for Module Loading
This feature allows you to add custom behavior to the module loading process. In this example, it logs the filename of each module being loaded.
const hook = require('node-hook');
hook.hook('.js', (source, filename) => {
console.log(`Loading module: ${filename}`);
return source;
});
require('./your-module');
Other packages similar to node-hook
pirates
The pirates package provides a similar functionality to node-hook by allowing you to hook into Node.js' require function. It is often used for transpiling code on the fly or adding custom behavior to module loading. Pirates is more focused on providing a simple and flexible API for hooking into the require function.
proxyquire
Proxyquire allows you to override dependencies during testing without modifying the original code. It is particularly useful for mocking modules in unit tests. Unlike node-hook, which hooks into the require function globally, proxyquire allows you to override dependencies on a per-require basis.
babel-register
Babel-register is a package that hooks into Node.js' require function to transpile ES6/ES7 code on the fly using Babel. It is specifically designed for transpiling code and is often used in development environments. Unlike node-hook, which can be used for various custom behaviors, babel-register is focused solely on code transpilation.
node-hook
Run source transform function on Node require
Install and use
npm install --save node-hook
Before loading desired .js files, install hook
require('node-hook');
function logLoadedFilename(source, filename) {
return 'console.log(' + filename + ');\n' + source;
}
hook.hook('.js', logLoadedFilename);
require('./dummy');
hook.unhook('.js');
remember: Nodejs caches compiled modules, so if the transform is not
working, you might need to delete the cached entry in require.cache
,
then call require(filename)
again to force reload.
Small print
Author: Gleb Bahmutov © 2013
License: MIT - do anything with the code,
but don't blame me if it does not work.
Support: if you find any problems with this module, email / tweet / open issue on Github