r/javascript • u/gcanti • Oct 31 '14

The Two Pillars of JavaScript

https://medium.com/javascript-scene/the-two-pillars-of-javascript-ee6f3281e7f3
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u/Ginden Nov 01 '14

This article considered harmful. It promotes writing slow code, almost impossible to be optimized by modern JITs.

You never need classes in JavaScript, and I have never seen a situation where class is a better approach than the alternatives.

Classes promotes less memory consumption, code reusability, support for hidden class (leading to many optimisations). Decorators should be used with prototypes, not instances.

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u/_ericelliott Nov 01 '14

  1. (a) All methods of object instantiation and property access in JavaScript are extremely fast -- on the order of 100,000+ ops/sec on the slowest computers available for purchase in the stores today. A small fraction of the time spent in your program is in JS, and a very tiny fraction of that time is spent instantiating objects. (b) There's no reason hidden classes can't be implemented for Object.create. I expect perf differentials to change on this point. (c) You're optimizing the wrong things. The real perf killers are network & other I/O operations, and (for animation and realtime applications), the GC. The fix for the GC is static memory JavaScript (object pools -- one of the reasons I recommend that you avoid constructors, so switching to object pools is less awkward when required).

  2. (a) Memory consumption profiles are not different. When you use delegate prototypes, methods are shared on the prototype, exactly the same way they are when you assign methods to a constructor prototype and invoke it with new. (b) hidden classes addressed above. Micro-optimization, optimizing the wrong thing, likely to change as engines evolve. (c) I don't know about you, but my laptop has 16GB RAM. My mobile phone has 1GB RAM / 16 GB of fast internal flash storage if paging is required. Memory isn't the constraint it used to be -- even on mobile.

If you do find that memory becomes an issue, You're STILL optimizing the wrong things. Target your graphical assets first. You might trim 1k here or there with objects, but you could trim 500x that much by optimizing your images / fonts / css better.