反应：ReferenceError：未定义obj

Question

我正在尝试将特定组件呈现到屏幕上，条件是我返回一个已解析的 Promise 数据为{result: "clear"} ，但是，尽管已将if条件放置在setTimeout()中，但我仍然得到obj is not defined ，即使 Promise 首先解析。

const useOnfidoFetch = (URL) => {
  const [token, setToken] = useState();
  const [id, setId] = useState();
  const [isClear, setIsClear] = useState(false);

  useEffect(() => {
    axios
      .get("http://localhost:5000/post_stuff")
      .then((response) => response.data.data.data.json_data)
      .then((json_data) => {
        console.log("this is the json data", json_data);
        const id = json_data.applicant_id;
        const token = json_data.onfido_sdk_token;
        setId(id);
        setToken(token);
      });
  }, [URL]);

  useEffect(() => {
    if (!token) return;
    console.log("this is working!");
    OnfidoSDK.init({
      token,
      containerId: "root",
      steps: [
        {
          type: "welcome",
          options: {
            title: "Open your new bank account",
          },
        },
        "document",
      ],
      onComplete: function (data) {
        console.log("everything is complete");
        console.log("this is the applicant id", id);
        axios
          .get("http://localhost:5000/post_id", {
            applicant_id: id,
          })
          .then((response) => {
            let obj;
            obj = response.data.data.data.json_data.result;
            setIsClear(true);
          });
        setTimeout(() => {
          if (obj === clear) {
            renderResult();
          }
        }, 3000);
      },
    });
  }, [id, token, setIsClear]);

  function renderResult() {
    return <Redirect to="/result" />;
  }
};

Answer 1

let关键字将它们的 scope 保留在声明它们的块中：

// the `obj` can only be called inside this scope
.then((response) => {
  let obj;
  obj = response.data.data.data.json_data.result;
  setIsClear(true);
});

参考： https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let#scoping_rules