Java: Parse JavaScript & Flag Errors

Question

I've been having terrible luck trying to get this to work, so I'm hopeful someone can help here.

In Java, I need to be able to take an HTML page with JavaScript within it and detect any JavaScript errors without, preferably without executing the JavaScript code.

I found this article: Javascript parser for Java

And I've attempted to figure out how I'm supposed to use Caja to do this, but I'm having a difficult time finding any documentation with working examples of anything close to what I'm doing.

As a result I took a look at Nashorn also referenced in that article. I found a few examples which show how to execute JavaScript code from Java, but this doesn't process the whole HTML page. Even then, the execution doesn't seem to include the ability to validate common JavaScript functions (e.g. It hadn't heard of "alert").

Can anyone recommend something that might be able to do what I want, and point me in the right direction for their documentation or give me an example?

Answer 1

jshint as a standalone product seems to be a good fit for this:

• it can run in java inside rhino (see https://github.com/jshint/jshint/)
• a nodejs package exists (see https://www.npmjs.com/package/jshint)
• it works with nashorn but it's quite tricky

I will only cover the technical difficulties around 3rd solution as I finally managed to make it work too...

Spoiler alert: "alert()" is not detected yet... Solution nb 2 will help there...

You first need to grab this specific release of jshint: https://github.com/jshint/jshint/releases/tag/2.4.4

Anything later than v2.7.0 will fail for now and I personally gave up patching intensively prototypes and namespaces... Releases from v2.4.4 until v2.6.3 work without modification but are limited in functionalities.

In the release notes, it's specifically written that "support for the Nashorn JavaScript engine" is working on this release. I'm using JDK8 nashorn 1.8.0_45 for this test.

Next step is to extract from this release this single file jshint-2.4.4/dist/jshint-rhino.js

Now you need to run nashorn/jjs in scripting mode and you need to be specific about the single file you wish to verify. In solution 2 (nodejs based) you can do multiple files or a complete hierarchy below a folder...

Create a simple file file.js:

function(){}

Now run the following command (please note the presence of -- ):

jjs -scripting jshint-rhino.js -- file.js

This will give you the following output:

Missing name in function declaration. (file.js:1:9)
> function(){}

So this covers the how to run jshint in a simple manner with nashorn... With the 3rd solution, at least you can find missing semicolons and several typical errors. But it's not a silver bullet and to me it's not a real alternative.

My personal preference would be to stick to solution 2 only. If you've the possibility to install either nodejs or iojs on your dev platform, go and grab https://www.npmjs.com/package/jshint. Not only will you be able to do more than the 3rd solution, you'll also be able to configure a jshintrc file as described at http://jshint.com/docs/