How do I keep hidden classes stable in V8?
Initialize objects with all their properties at creation. Do not add properties later. Do not use delete. This keeps the hidden class stable, which lets V8 optimize property access and function performance.
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More FAQs in V8 Hidden Classes Explained: What They Are and Why They Matter
V8 assigns a hidden class to each object to track its shape (which properties it has). When you add or delete a property, V8 creates a new hidden class. Hidden classes are how V8 optimizes property access for speed.
Because V8 uses hidden classes to optimize property access. If the hidden class is stable, V8 can inline property access for speed. If it changes (add or delete properties after creation), V8 deoptimizes and slows down.
Only if created the same way: same properties in the same order. Two objects created differently (different property order) create different hidden classes, which prevents V8 from sharing optimized code between them.
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