als-require

als-require

als-require is a lightweight utility that enables the importation and modification of CommonJS modules before execution in both browser and Node.js environments.

Capabilities of als-require:

• Utilize CommonJS modules in the browser, complete with all dependencies and access to module functionalities.
• Employ a unified context object across all modules.
• Modify the code of each module before it is executed.

Where it can be particularly useful:

• Enables the use of the same codebase on both server and browser, facilitating seamless integration.
• Allows for on-the-fly code rendering without the need for building a separate bundle.

Installation

To install als-require, use npm:

npm install als-require

Importing

Import in nodejs:

const Require = require('als-require')
const module = Require.getModule('./some/path')

Import in browser:

<script src="/node_modules/als-require/require.js"></script>
<script>
   Require.getModule('./some/path')
   .then(module => {
      // ...
   })

   // or    Require.getModule('./some/path')
   require('./some/path').then(module => {
      // ...
   })

</script>

Usage

als-require has two files for NodeJS and browser which has same structure and api. Each file includes Require class with folowing structure:

class Require {
   static getModule(path, context,contextName) {}
   static contents = {}
   constructor(path, context = {},contextName) {
      this.modules = {}
      this.contents = {}
      this.path = path
      this.context = context
   }
   getContent(path = this.path, from = Require.relativePath) {}
   build(modules = this.modules,context,contextName = this.contextName) {}
}

The structure above describes only properties and methods for usage, without additional properties and methods which used as private methods.

The constructor gets two arguments: path and context.

• path (String): relative path to module for require
• context (Object): shared object which will be available in all modules
• contextName (String): Name for context variable (default context)

Here explanation what each method and property used for:

• Require.getModule - quick way to get contents and build them in one step
  • returns new instance of Requires with ready contents, modules and result
  • The method is sync for NodeJS and async for browser
• Require.contents - includes modules contents and their children list and used as cache
• require.getContent() - used for reading module file's contents
  • Adding content to Require.contents and to require.contents
  • The browser version is async and NodeJS version is sync
• require.build() - builds all modules results
  • parameters:
    • modules - you can add custom modules (for example modules from backend for same path)
    • context - private context for curent build (will includes instance.context properties too)
    • contextName - private conteName for curent build
• require.modules - includes all module's results after build
• require.result - has the main module result (export) after build

Node.Js

const Require = require('als-require')
const path = './relative/path/to/module'
const context = {} // shared object for all modules empty object by default
const mod = new Require(path,context)
mod.getContent() // reading all modules
for(const path in mod.contents) {
   mod.contents[path] = mod.contents[path] // modify if needed
}

mod.build() // build the result
mod.result // includes the result of main module
mod.modules // object with all module`s results {relativePath:moduleResult,...}

If you want to use node modules libraries, you need to specify relative path.

Browser

<script src="/node_modules/als-require/require.js"></script>
<script>
   const path = './relative/path/to/module'
   const context = {} // shared object for all modules empty object by default
   const mod = new Require(path,context)
   const promise = mod.getContent() // fetching all modules
   promise.then(mod => {
      for(const path in mod.contents) {
         mod.contents[path] = mod.contents[path] // modify if needed
      }
   
      mod.build() // build the result
      mod.result // includes the result of main module
      mod.modules // object with all module`s results {relativePath:moduleResult,...}
   })
</script>

Require node_modules packages and node modules

In case of path which not starts with ., Require will look for file in node_modules (by checking in package.json). If such package not found (for example require('fs')), result for this package will return null.

const somePackage = require('some-package');
const somePackage1 = require('./node_modules/some-package/index.js');
const fs = require('fs');

module.exports = {somePackage,somePackage1,fs}

In case above somePackage and somePackage1 should return the package, but fs, should return null.

Pay attention, using './node_modules/some-package/index.js' instead 'some-package', you save extra request/readFile for looking the filename.

Context Usage

The context object is a shared space accessible by all modules loaded by als-require. This allows modules to read and write shared data, enabling more interactive and dynamic module behaviors.

Make sure you are using the context for static value (like constants and common variables and functions) and not dynamic, cause it available to all require's results.

Error Handling

als-require throwing errors in case of cyclic dependencies and if some module throwing error.

For the case of module's error, Require adds to stack modules paths which has called.