Prototype yet to release compressed version of it’s framework. And still, when I will make a compressed version of Prototype version 1.7.0.0, the same error appears in 2 places, near line 1215 and line 1916. After adding the semicolon at that line, the compressed Prototype work flawlessly.

Line 1213-1215, add semicolon in the last line

  var CONCAT_ARGUMENTS_BUGGY = (function() {
    return [].concat(arguments)[0][0] !== 1;
  })(1,2);

Line 1909-1916, add semicolon in the last line

Element._purgeElement = function(element) {
  var uid = element._prototypeUID;
  if (uid) {
    Element.stopObserving(element);
    element._prototypeUID = void 0;
    delete Element.Storage[uid];
  }
};

In the download file below there are two file of Prototypejs: minified (only) version (120kb), and minified+encoded version (60kb), where the standard Prorotypejs is about 160kb.

• Download Prototype 1.7.0.0 (3) (latest)