I happened upon an open source tool for refactoring JavaScript that has been useful. The tool is named Grasp, and it enables searching and replacing on the AST (abstract syntax tree) of your JavaScript code. This is powerful because instead of finding or replacing bits of text throughout your codebase, you can replace only identifiers, for instance. Or you could find matching blocks of code that are spread across lines, since we look at the entire syntax tree, not the text representation of it.

There is a fantastic blog post on the Grasp website. It provides several examples of common refactorings (rename variable, changing a function to accept an arguments hash instead of adding another parameter, etc.) It really does a great job of showing why standard tools like sed and grep fall short during refactoring. The examples are clear and provide good starting points for your own refactorings.

I’d love to see a Vim plugin/wrapper for Grasp. Especially if it could do simple JavaScript refactorings (extract method/function, rename variable, to name a few.) I feel a little safer using Grasp than I do with sed, which can corrupt my git repository if I foolishly invoke it incorrectly. My typically workflow is to run a command to search for the text that I want to replace, then run it inline, and then run git diff to see any potential replacement anomalies.