Obfuscated js throws error: "Uncaught SyntaxError: Illegal return statement"

I am using javascript-obfuscator 0.10.0-beta.8, and I have been obfuscating my js from the command line, with good success, for a few months now. But as of the past week or so, many of my resultant obfuscations error out inside my Chrome extension. I haven’t touched javascript-obfuscator, haven’t updated it, nothing. Also I haven’t changed the way I’m calling it from cmd-line, nor changed any params.

Here is the error I have been getting: Uncaught SyntaxError: Illegal return statement. And here is the obfuscated block of code that triggers it:

if (_0x4423('0x7') === 'mJc') {
     zingLog(_0x4423('0x8'));
} else {
      return !![];
}

The return !![]; seems to be throwing the error. Both Chrome and JSNice point at the same line. When I encountered this 3-4 days ago, I had no idea what to do about it. I ended up re-obfuscating my files 2 or 3 more times, and after that – PRESTO – the error was gone. I wish I had taken a diff so I could know what changed. But that was another puzzling thing: how can I get different obfuscated results after changing nothing, no cmd-line params, no source code, etc? It seems as though the obfuscator generates different results each time it runs??

Here is how I’m calling the obfuscator:

node "C:\javascript-obfuscator.js" "myfile.js" --output "C:\obfuscated.js" --compact true --controlFlowFlattening true --controlFlowFlatteningThreshold 0.75 --deadCodeInjection true --deadCodeInjectionThreshold 0.4 --mangle false --rotateStringArray true --selfDefending true --stringArray true --stringArrayThreshold 0.75 --stringArrayEncoding false --unicodeEscapeSequence false

That always executes with no errors, and as mentioned, in the past the resulting obfuscations work great, and ran fine in Chrome. I am currently using Chrome Version 61.0.3163.79 (Official Build) (64-bit). That’s the latest update as of 9/12/2017, but the previous version I was on (60.xxx - before today) threw the same error.

Is this a bug in the obfuscator? A bug in the browser? Can changing a cmd-line option solve this? My entire obfuscated file is over 1500 lines so it seems ill-advised to post all of it here, but I can if necessary. Please help.

Thanks in advance.

[HerrimanCoder]

That works great now. Thanks so much!

[lock[bot]]

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