Plain Code

jQuery.extend({
    compareVersions : function (have, require) {
        if (typeof require == 'undefined') {
            require = have;
            have = jQuery.fn.jquery;
        }
        
        function parts(val) {
            // Expecting following format 1.2.3rc1, 1.2.4a, etc.
            return val.replace(/[a-z]+/i, function(m) { 
                return '.' + (m == 'pre' ? '0pre' : m);
            }).split('.');
        }
        
        if (require == have) return 0;
        
        var latest = parts(have), 
            required = parts(require), 
            i = 0;

        while (latest[i] && required[i]) {
            if (latest[i] < required[i]) {
                return -1;
            } else if (latest[i] > required[i]) {
                return 1;
            }
            i++;
        }

        return (latest[i]
                ? (/^d/.test(latest[i]) ? 1 : -1)
                : (/^d/.test(required[i]) ? -1 : 1));
    },
    hasVersion : function() { 
        var ok = this.compareVersions.apply(this, arguments);
        return (ok === 0 || ok === 1); 
    }
});