Should I use arguments or rest parameters in hot Node.js code?
Prefer rest parameters (...args) over the arguments object in hot code. Modern V8 handles arguments better, but rest parameters are clearer and optimize more reliably, especially in performance-critical code.
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More FAQs in V8 Performance Tips for Node.js Developers
Profile first to find the real bottleneck, keep hot functions monomorphic (consistent argument types), initialize objects fully (avoid hidden class changes), avoid delete and with, keep arrays homogeneous, and prefer rest parameters over arguments in hot code.
Because premature optimization based on guesses wastes time. Use the Node.js inspector and CPU profiler to find what is actually slow, then optimize the real bottleneck. Measure first, always.
Because delete changes an object's hidden class, which deoptimizes the code in V8. Set properties to undefined instead, or restructure the object differently, to keep the hidden class stable and V8 optimizations intact.
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