Method onsubmit

code/solutions/21_2_comment_field_resets.mjs:19–26

(event)

      this.comments,
      elt("form", {
        onsubmit(event) {
          event.preventDefault();
          let form = event.target;
          dispatch({type: "newComment",
                    talk: talk.title,
                    message: form.elements.comment.value});
          form.reset();
        }
      }, elt("input", {type: "text", name: "comment"}), " ",
          elt("button", {type: "submit"}, "Add comment")));
    this.syncState(talk);