Insert a string before the extension in a filename

Question

How can I insert a string before the extension in an image filename? For example, I need to convert this:

../Course/Assess/Responsive_Course_1_1.png 

to this:

../Course/Assess/Responsive_Course_1_1_large.png 

Answer 1

If we assume that an extension is any series of letters, numbers, underscore or dash after the last dot in the file name, then:

filename = filename.replace(/(\.[\w\d_-]+)$/i, '_large$1'); 

Answer 2

None of the answers works if file doesn't have extension. Here's a solution that works for all cases.

function appendToFilename(filename, string){     var dotIndex = filename.lastIndexOf(".");     if (dotIndex == -1) return filename + string;     else return filename.substring(0, dotIndex) + string + filename.substring(dotIndex); }