Using const/let instead of var can make JavaScript code run 10× slower in Webkit
Looks like the JavaScriptCore people are on it :)<p>As an aside, I’ve been seeing a number of articles show up that basically go like “Chrome implements x efficiently but semantically equivalent y poorly, you should use always use x”. I really hope we don’t end up with JavaScript code being written to be optimized well on one particular implementation of a JavaScript engine…it’s interesting to see this in this area specifically because other VMs (e.g. Java) have knobs you can turn yourself but with JavaScript your code runs without much input on your side, so methods to influence the VM are much more specific…