Prepros: Error minifying JS

Question

I have a file script/qArray/questions.js and here's the thing: it won't minify. This is all the code I have in it:

var QuizCard = function (question, options, answer, explanation) {

}

And voila comes out the error.

top_retain.indexOf() is not a function. That's what it said.

What's going on?

Edit: Here's something, this code worked perfectly well yesterday. Today, it seemed to update (from 6.0.13 to 6.0.14) and doesn't work anymore. Changelog: Fixed an error while minifying some js files

Answer 1

It says unknown to process file, check if the file path is correct then check by determining if the code is in error then -> go step by step also knowing which minifying code base you're using can help :),

sorry if this seems a little redundant. :D but i ran your code another online minifier and it worked fine :)