code: @Override
      public boolean contains(final String varName) {
          return runWithContext(new RhinoCallable<Boolean, RuntimeException>() {
              @Override
              protected Boolean doCall(Context cx, Scriptable scope) {
                  return scope.get(varName, scope) != null;
              }
          });
      }
docs: /* (non-Javadoc)
  @see minium.script.rhinojs.JsEngine#contains(java.lang.String)