render() {
const users = this.state.words.map( key => <li> {key} </li>)
return (
<div className="todo-item">
{users}
</div>
)
Objects are not valid as a React child (found: object with keys {key}). If you meant to render a collection of children, use an array instead.
При следующих вопросах обязательно учту ваши замечания!