The Persistent Divide: Unpacking JavaScript's Module System Struggles

The Unfinished Transition in JavaScript's Foundation

Boris Cherny's recent examination of JavaScript's module system reveals a persistent architectural friction point that continues to impact developers years after ECMAScript Modules (ESM) standardization. His experience returning to JavaScript/TypeScript development highlights recurring errors like ERR_REQUIRE_ESM and SyntaxError: Cannot use import statement outside a module – symptoms of an ecosystem struggling with its own evolution. At the core lies a critical question: Why has the transition from CommonJS to ESM remained so fraught despite clear technical advantages?

Historical Context and Fractured Adoption

The module system's evolution traces JavaScript's growth from browser scripts to full-stack language. Early solutions like AMD and RequireJS gave way to CommonJS dominance, particularly in Node.js environments. ES Modules arrived in 2015 promising static analyzability, asynchronous loading, and future-proof syntax – yet implementation introduced new complexity. Node.js adopted dual pathways: file extensions (.mjs/.cjs) versus package.json declarations (type=module), creating a combinatorial explosion of interoperability scenarios.

Cherny's data-driven analysis quantifies the adoption gap:

• Only 9-27% of JavaScript/TypeScript projects declare ESM via package.json
• Less than 6% utilize ESM-specific file extensions (.mjs/.cjs)

These metrics, gathered from top GitHub repositories and npm packages, reveal stalled progress five years after Node's ESM support. The consequence is a fragmented landscape where developers constantly negotiate between systems, often through error-driven trial and error.

The Interoperability Tax

The coexistence paradigm imposes tangible costs:

1. Cognitive overhead: Developers must master two module systems and their edge-case interactions
2. Toolchain complexity: Compilers (Babel, TypeScript) require intricate configurations to bridge systems
3. Runtime constraints: Dynamic require() clashes with ESM's static structure
4. Editor/IDE challenges: Static analysis tools struggle with hybrid codebases

This friction contradicts JavaScript's reputation for developer ergonomics, particularly affecting newcomers and those transitioning between ecosystems.

Pathways Toward Resolution

Cherny proposes concrete ecosystem-level interventions:

1. File extension consolidation: Deprecate .mjs/.cjs in favor of original extensions (.js/.ts) with package.json configuration
2. Default ESM for new projects: npm/yarn/pnpm init should set "type": "module" automatically
3. Registry enforcement: npm could require explicit module declarations for new packages
4. Ecosystem modernization: Coordinated efforts to migrate high-impact libraries to ESM
5. Node.js roadmap: Phased CommonJS deprecation to incentivize migration

These proposals target the root coordination challenges rather than technical limitations. The emphasis on package.json configuration acknowledges developers' preference for centralized settings over file-specific conventions.

Counterbalancing Considerations

Potential counterarguments deserve examination:

• Backward compatibility: Enterprise codebases and legacy environments require CommonJS support
• Incremental migration: Sudden ecosystem shifts could destabilize dependency graphs
• Tooling maturity: Early ESM implementations in Node.js had limitations that justified transitional solutions
• Author autonomy: Library maintainers may resist mandated migration timelines

Notably, some complexity stems from valid technical constraints: CommonJS's runtime flexibility versus ESM's static structure creates fundamental incompatibilities that no tooling can perfectly abstract.

Toward Cohesive Module Futures

The ESM transition represents more than syntactic preference – it's foundational infrastructure work. While Cherny's data suggests stalled adoption, it also reveals opportunity for coordinated ecosystem action. Package managers and runtime maintainers possess unique leverage to reduce friction through:

• Sensible defaults for new projects
• Clear migration pathways
• Enhanced diagnostic messaging

The solution space requires balancing technical progress with ecosystem stability. As JavaScript continues expanding into new domains – from edge computing to WebAssembly integration – resolving this longstanding divide becomes increasingly urgent. Unified module handling would free cognitive resources for higher-order innovation rather than perpetual configuration archaeology.

Cherny's analysis ultimately underscores how ecosystem coordination challenges can outweigh technical ones. The path forward lies not in new specifications, but in concerted implementation strategy across Node.js, npm, and the broader JavaScript community.