V8 uses Turbofan to optimize some functions that Crankshaft couldn't. As of July, `for-of` and `with` were optimized with Turbofan, but not `try-catch`: http://

V8 uses Turbofan to optimize some functions that Crankshaft couldn't. As of July, `for-of` and `with` were optimized with Turbofan, but not `try-catch`: http://v8project.blogspot.com/2015/07/v8-45-release.html http://v8project.blogspot.com/2015/07/v8-45-release.html Since then there's been work on Turbofan support for `try-catch`, but I can't tell if it's been shipped and enabled, so I could be wrong.