> For example preallocating arrays. You don't need a benchmark to tell you it will be faster because it literally can't not be. This assertion is false for Jav

> For example preallocating arrays. You don't need a benchmark to tell you it will be faster because it literally can't not be. This assertion is false for JavaScript arrays in the v8 engine in some contexts. Preallocation of a JS array causes the engine to make a heterogeneous array, which is more expensive because it's an object under-the-hood. Allocating the array using repeated `push` calls of homogeneous data lets the engine know it's a homogeneous-type array, which is an "exotic object" that can use more optimal representations under-the-hood. (Faster than both is preallocating a homogeneous array, although that of course requires us to know what kind to preallocate). This is another example of where premature optimization can lead a developer astray. Abstractions are far too complicated these days, and it's too easy to guess wrong without hard data. https://dev.to/henryjw/populating-a-pre-allocated-array-slower-than-a-pushing-to-a-regular-array-4l43 https://dev.to/henryjw/populating-a-pre-allocated-array-slow...