jsify function
Returns the JS representation from Dart Object.
This function is identical to the one from 'dart:js_util' with only
difference that it handles basic types (String, num, bool and null.
See also:
Implementation
dynamic jsify(Object dartObject) {
  if (_isBasicType(dartObject)) {
    return dartObject;
  }
  return js_util.jsify(dartObject);
}