javascript - React JS - 请求的资源上不存在 'Access-Control-Allow-Origin' header 。跨源资源错误

Question

我正在 React Web 应用程序中使用 Fetch 进行 API 调用(在另一个域上运行)。我收到错误以下错误。

Access to fetch at'--------API URL---------' from origin 'http://localhost:3000' has been blocked by CORS policy:
Response to preflight request doesn't pass access control check: No'Access-Control-Allow-Origin' header is present on the requestedresource. If an opaque response serves your needs, set the request'smode to 'no-cors' to fetch the resource with CORS disabled.

我还在 Stack Overflow 上阅读了关于同一问题的几个答案，标题为“Access-Control-Allow-Origin”，但仍然不知道如何解决这个问题。我不想在 Chrome 中使用扩展程序或使用临时黑客来解决这个问题。请提出解决上述问题的标准方法。

我的代码如下所示:

{
        return fetch('-----------API URL--------',
        {   method:'GET',
            mode: 'cors',
            headers:{
                'Access-Control-Allow-Origin':'*'
            },
        })
        .then((response) => response.json())
        .then((responseJson) => {
            console.log(responseJson.ALLORDERSRX);
            this.setState({
                isLoading: false,
                dataSource: responseJson.ALLORDERSRX,
            }, function(){
                
            });
        })
        .catch((error) =>{
            console.error(error);
        });

    }

Answer 1

const proxyurl = "https://cors-anywhere.herokuapp.com/";
const url = 'https://api.liveconnect.in/backend/web/erpsync/get-all-orders?data=dbCode=UAT04M%7Cidx=100%7CuserId=6214%7Cres_format=1'; // site that doesn’t send Access-Control-*
fetch(proxyurl + url).then((resp) => resp.json())
  .then(function(data) {
    console.log(data);
  })
  .catch(function(error) {
    console.log(error);
  }); 

从这里找到:No 'Access-Control-Allow-Origin' header is present on the requested resource—when trying to get data from a REST API