ExecJS::ProgramError: Unexpected token punc «(», expected punc «:» when running rake assets:precompile on production

Question

When deploying my Rails app I get the following error:

rake aborted!
   ExecJS::ProgramError: Unexpected token punc «(», expected punc «:» (line: 15, col: 14, pos: 265)

   Error
   at new JS_Parse_Error (/tmp/execjs20150524-4411-1p45n63js:2359:10623)
   at js_error (/tmp/execjs20150524-4411-1p45n63js:2359:10842)
   at croak (/tmp/execjs20150524-4411-1p45n63js:2359:19086)
   at token_error (/tmp/execjs20150524-4411-1p45n63js:2359:19223)
   at expect_token (/tmp/execjs20150524-4411-1p45n63js:2359:19446)
   at expect (/tmp/execjs20150524-4411-1p45n63js:2359:19584)
   at /tmp/execjs20150524-4411-1p45n63js:2359:28513
   at /tmp/execjs20150524-4411-1p45n63js:2359:19957
   at expr_atom (/tmp/execjs20150524-4411-1p45n63js:2359:27269)
   at maybe_unary (/tmp/execjs20150524-4411-1p45n63js:2359:30019)new JS_Parse_Error ((execjs):2359:10623)
   js_error ((execjs):2359:10842)
   croak ((execjs):2359:19086)
   token_error ((execjs):2359:19223)
   expect_token ((execjs):2359:19446)
   expect ((execjs):2359:19584)
   (execjs):2359:28513
   (execjs):2359:19957
   expr_atom ((execjs):2359:27269)
   maybe_unary ((execjs):2359:30019)

The file in question is valid, it works on localhost. I also tried running rake assests:precompile on localhost, it all passes. Finally, I tried to remove the content from the file, git push and redeploy - still got the same error. Only completely removing the file and re-deploying helps.

Would appreciate any ideas.

Answer 1

Here I found help for the same problem you had.

Run rails console and:

JS_PATH = "app/assets/javascripts/**/*.js"; 
Dir[JS_PATH].each do |file_name|
  puts "\n#{file_name}"
  puts Uglifier.compile(File.read(file_name), harmony: true)
end

It will show you the file and the line where the Uglifier is making the problem.

Answer 2

I suspect, in that js file, you have something like the following:

var User = {
    getName() {
        alert("my name");
    }
}

Replacing it with the right format,

var User = {
    getName: function() {
        alert("my name");
    }
}

worked for me.

Error is clearly saying, it's expecting ":" but it found "(".

Answer 3

Just encounter the same issue.

My case is someone used syntax that's only support since ES2015, ex

function someThing(param = true) {
    // do something here
};

while this is not supported in our environment.

And the error messages is actually generated by Uglifer.