FrontendMasters - JavaScript VM Under the Hood

Why is it called Virtual Machine? How is JavaScript translated into machine code? And why should I care? What makes code monomorphic or polymorphic, and why can the difference in speed be 100x? What is meant by deoptimization, and how does it happen? What are holey arrays, and why should I care? Why can == be 15 x slower than === and more.

In this workshop, we will do a deep dive into how JavaScript Virtual Machine works and what happens under the hood. How do I debug my application performance and gain insight as to what the Virtual Machine is doing? All of this is useful to know when your code is running in a hot path and you want to get maximum performance, or it's just cool to know how things work under the hood.


By participating along with us in the workshop, you'll learn:

• Get a mental model of how Physical Machines (CPUs) work
• Learn which features of JS are created using a VM (virtual machine)
• Understand calling conventions, inlining and deopt
• Use object layout, polymorphism and inline caches