为何多数游戏/图形JS代码仍使用var而非现代语法？

Great question! I’ve been building with JavaScript for years too, and I totally get what you’re noticing—when diving into WebGL and game engine ecosystems like Three.js, Babylon.js, PixiJS, Phaser, or stack.gl examples, it feels like modern ES6+ features (arrow functions, let/const, Promises) are often sidelined in favor of var and callback-based code. Let’s break down the key reasons behind this:

• Backward Compatibility is Non-Negotiable
  These libraries serve an enormous range of devices, from cutting-edge desktops to older mobile phones, embedded systems, and legacy web viewers. Many of these environments don’t fully support ES6+ syntax—using arrow functions or const could break code for a significant portion of users. Sticking to var and callbacks ensures the code runs reliably everywhere, without requiring heavy transpilation that might bloat the library or introduce unexpected bugs in performance-critical paths.

• Legacy Codebases with Deep, Battle-Tested Roots
  Most of these projects launched long before ES6 became mainstream (Three.js, for example, started in 2010). Rewriting an entire codebase—often millions of lines of complex graphics code—to adopt modern syntax is a massive, high-risk undertaking. It’s not just a simple find-and-replace for var; refactoring callback patterns to Promises or async/await could introduce breaking changes for existing developers who rely on the library’s current API. Maintainers prioritize stability and backward compatibility over adopting the latest syntax trends.

• Performance and Low-Level Control
  Graphics programming demands tight control over execution order, memory usage, and performance—especially in hot loops like animation or render cycles. Early on, modern JS features like arrow functions had subtle performance differences compared to regular functions in these critical paths. Callback patterns also offer more predictable execution flow when dealing with WebGL’s state machine, which is crucial for avoiding rendering glitches. While modern JS engines have optimized these features extensively, the proven, predictable patterns of callbacks and var still hold sway in performance-sensitive code.

• Ecosystem and Documentation Consistency
  The examples, tutorials, and community plugins for these libraries need to align with the core codebase. If the library uses callbacks, switching docs to Promises would create confusion for users trying to match official examples with the source code. Plus, years of community content uses the callback style—changing syntax would fragment the ecosystem and force developers to learn two conflicting patterns. Maintainers keep docs and examples consistent with the library’s core to reduce friction for new and existing users.

That said, you will start to see modern syntax creeping into newer parts of these libraries! As browser support improves, maintainers gradually refactor non-critical modules to use let/const, and some even offer optional Promise-based APIs. But the core remains callback-heavy and reliant on older syntax to prioritize the unique needs of graphics programming and their broad user base.

内容的提问来源于stack exchange，提问作者Lesbaa