Partial duplicate of this
Notes: I already use JSLint extensively via a tool I wrote that scans in intervals my current project directory for recently updated/created .js files. It's drastically improved productivity for me and I doubt there is anything as good as JSLint for the price (it's free).
That said, is there any analysis tool out there that can find repetitive or near-duplicate code blocks, the goal being to make it easier to find opportunities to consolidate large files or small/medium sized projects?
Our CloneDR is a tool for finding exact and near-miss cloned code blocks for a variety of languages. It will find duplicates in the same file or across literally thousands of files if you have them. You don't have to provide it with any guidance; it can find the cloned code by itself. And it won't be fooled by different indentation or line breaks, or even consistent renaming of identifiers
It does support JavaScript, even if it isn't clear from the website.
You can see sample clone reports for a variety of langauges at the website.
May not be exactly what your after, but Google's Javascript optimizer is worth a look.