javascript - 未处理的拒绝(类型错误): Cannot read property 'map' of undefined

Question

我从 developers.themoviedb.org 获取对象，但真的很失望有什么问题。
对象被发送到浏览器，但我不明白如何把它扔给我。
我很困惑，需要帮助
如果在中间件中我写 let arr = JSON.parse(response).results; 也是一个错误:

Unexpected token o in JSON at position 1

response with object in browser

数据.service.js

export const getData = (url) => new Promise((resolve, reject) => {
const request = new XMLHttpRequest();
request.open('GET', url);
request.onload = () =>
    (request.status === 200) ?
        resolve(JSON.parse(request.response).results) :
        reject(Error(request.statusText))
  request.onerror = (err) => reject(err)
  request.send();
});

电影.middleware.js

export const moviesMiddleware = store => next => action => {
if (action.type === FETCH_MOVIES_START) {
    getData(popularMovies).then((response) => {
        let arr = response.results;
        let movies = arr.map((item) => {
           return new MovieEntity(item);
        });
        let data = movies;
        store.dispatch({
            type: FETCH_MOVIES_SUCCESS,
            payload: data
        });
    });
  }
  return next(action);
}

电影.action.js

export function fetchMovies() {
return {
    type: FETCH_MOVIES_START
 }
}

Answer 1

您的数据已经是一个对象。无需解析它。每次解析之前检查参数的 typeOf 是否为字符串。 ------编辑-----

也可以尝试:

  resolve(
   if(typeOf(request.response)=='string')
    JSON.parse(request.response).results 
   else request.response.results
   )

在movies.middleware.js中更改如下

export const moviesMiddleware = store => next => action => {
if (action.type === FETCH_MOVIES_START) {
    getData(popularMovies).then((response) => {
        let arr = response;
        let movies = arr.map((item) => {
           return new MovieEntity(item);
        });
        let data = movies;
        store.dispatch({
            type: FETCH_MOVIES_SUCCESS,
            payload: data
        });
    });
  }
  return next(action);
}

问题是，您正在使用 request.response.results 解析 Promise，然后您再次以与 response.result 相同的方式访问它，或者返回 request.response 或更改上面的访问 response 。