Function has_str 

pub fn has_str<T>(
    target: &Object<T>,
    property_key: &JsString,
) -> Result<bool, JsValue>
where
    Object<T>: ErasableGenericBorrow<Object<JsValue>> + EncodeTypeDef,
    for<'__wry_bindgen> &'__wry_bindgen Object<T>: BinaryEncode,

The static Reflect.has() method works like the in operator as a function.

MDN documentation