Project Classtrophobic can work on older browsers too.

No class or Proxy used in here, and the only caveat is that subclasses with a constructor must return the super instance.

var List = Class({
  extends: Array,
  constructor: function () {
    // super might promote current instance
    var self = this.super();
    // be sure you use the right reference
    self.push.apply(self, arguments);
    // and remember to return it
    return self;
  },
  push: function () {
    // constructor a part, everything else is the same
    this.super.push.apply(this, arguments);
    // make push chainable for demo purpose
    return this;
  }
});

You can test live both classtrophobic and classtrophobic-es5. If the page turns out green, you're good to go!

The main difference is that ES5 version has a greedy runtime when it comes to super usage, while this original version uses real classes and delegate to Proxy access the super resolution, working only when a method is accessed and per single method, as opposite of runtime setup for all methods in the es5 case.

^{_{Luckily overrides are not the most frequent thing ever.}}

At least the annex B __proto__ accessor should be there. This means pretty much every Mobile browser and every Desktop one, starting from IE11.