Reuse JS code between browser and server with dependency on pngjs

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Summary

The problem at hand is how to reuse JavaScript code between browser and server environments when there’s a dependency on pngjs, a library for working with PNG images. The goal is to move a new class, MyNewClass, into an existing module, MyExistingModule, in a way that allows the module to work seamlessly in both environments.

Root Cause

The root cause of this issue is the difference in how modules are loaded and dependencies are managed in browser and server (Node.js) environments. In the browser, scripts are loaded via <script> tags, and dependencies like pngjs can be included from a CDN. In contrast, Node.js uses a module system where dependencies are imported using require or import statements.

Why This Happens in Real Systems

This issue arises in real systems due to the following reasons:

  • Different execution environments: Browser and server environments have different ways of loading and executing JavaScript code.
  • Dependency management: Managing dependencies like pngjs differently in each environment can lead to conflicts and compatibility issues.
  • Code reuse: The desire to reuse code across environments without duplicating effort or creating environment-specific implementations.

Real-World Impact

The impact of not addressing this issue includes:

  • Code duplication: Maintaining separate implementations for browser and server environments, leading to increased development and maintenance costs.
  • Inconsistent behavior: Potential for different behavior or bugs in each environment due to differing implementations or dependency versions.
  • Complexity: Increased complexity in managing dependencies and ensuring compatibility across environments.

Example or Code

// MyNewClass.js (browser environment)
import { PNG } from 'pngjs/browser';
class MyNewClass {
  #myPng;
  constructor() {
    this.#myPng = new PNG();
    // Do things that a MyNewClass does.
  }
}

// MyNewClass.js (server environment)
import { PNG } from 'pngjs';
class MyNewClass {
  #myPng;
  constructor() {
    this.#myPng = new PNG();
    // Do things that a MyNewClass does.
  }
}

How Senior Engineers Fix It

Senior engineers address this issue by using techniques such as:

  • Dynamic imports: Using dynamic imports to load dependencies conditionally based on the environment.
  • Environment-specific modules: Creating separate modules for each environment, each with its own dependency management.
  • Dependency injection: Passing dependencies like pngjs as parameters to classes or functions, allowing for flexibility in dependency management.

Why Juniors Miss It

Junior engineers may miss this issue due to:

  • Lack of experience: Limited experience with cross-environment development and dependency management.
  • Insufficient understanding: Not fully grasping the differences between browser and server environments and how they impact code reuse and dependency management.
  • Overlooking complexity: Underestimating the complexity of managing dependencies and ensuring compatibility across environments.