Something

element foo implements JavascriptConstructor {
  public function js() {
    return jsprintf('new FooController(%d, %d)', 1, 2);
  }

  protected function render() {
    $root = <div />;
    onloadRegister('%O.init(%O)', $this, $root);
    return $root;
  }
}

$foo = <foo />;
onloadRegister('GiveMeAFoo(%O)', $foo);
echo $foo;

---
JSCC={
  ctors: [function() {
    return new FooController(1, 2);
  }],
  refs: {},
  get: function(key) {
    if (refs[key]) {
      return refs[key];
    } else {
      refs[key] = ctors[key]();
      delete ctors[key];
      return refs[key];
    }
  }
}
<script>GiveMeAFoo(JSCC.get(1))</script>
<div id="randomid" />
<script>JSCC.get(1).init($('randomid'))</script>