Sorting strings in reverse order with backbone.js

You could:

• grab the char code for each character in the string,
• subtract each value from 0xffff (the maximum return value of string.charCodeAt),
• use String.fromCharCode to turn that back into string of “negated” characters

and that will be your sorting key.

chapters.comparator = function(chapter) {
    return String.fromCharCode.apply(String,
        _.map(chapter.get("title").split(""), function (c) {
            return 0xffff - c.charCodeAt();
        })
    );
}

And voila:

> console.log(chapters.pluck('title'));
["The Middle", "The End", "The Beginning"]

Note: if your comparison strings are long (as in 65 kb or more), you may run into trouble (see Matt’s comment below). To avoid this, and speed up comparisons a bit, just use a shorter slice of your comparison string. (In the above example, you could go for chapter.get("title").slice(0, 100).split("") instead.) How long a slice you need will depend on your application.