How we made JSON.stringify more than twice as fast

JSON.stringify is a core JavaScript function for serializing data. Its performance directly affects common operations across the web, from serializing data for a network request to saving data to localStorage . A faster JSON.stringify translates to quicker page interactions and more responsive applications. That’s why we’re excited to share that a recent engineering effort has made JSON.stringify in V8 more than twice as fast . This post breaks down the technical optimizations that made this improvement possible. A Side-Effect-Free Fast Path # The foundation of this optimization is a new fast path built on a simple premise: if we can guarantee that serializing an object will not trigger any side effects, we can use a much faster, specialized implementation. A "side effect" in this context is anything that breaks the simple, streamlined traversal of an object. This includes not only the obvious cases like executing user-defined code during serialization, but also more subtle internal op