Returns the value associated with property from the proxied JavaScript
object.
The type of property must be either String or num.
Source
E operator [](index) {
  if (index is int) {
    _checkIndex(index);
  }
  return super[index];
}
    Returns the value associated with property from the proxied JavaScript
object.
The type of property must be either String or num.
E operator [](index) {
  if (index is int) {
    _checkIndex(index);
  }
  return super[index];
}