Checking that a filename does not end with "Com.js"
By mechanical transformation, I arrive at:

function checkFile(file) {
    return file == null || !jQuery.endsWith(file, "Com.js");
}


The use of === strict equality checking is not necessary; == lumps null and undefined together.

I have my doubts about the whole function, though, as the function name gives no indication that it's going to check whether its argument ends in "Com.js".