How to format a base64 encoded string to jslintable lines of x characters?

I have to lint a number of files which include images as base64 strings.

Of course I can break them into the correct line format by hand, but...

Question:

Are there any online converters which break strings into "JavaScript usable" lines of n characters? I was trying to use textmechanic but it will still require me to wrap lines in "[line]" + which becomes cumbersome rather quickly.

Thanks!