CORS policy Error when trying to fetch information from an API [duplicate]-CodePudding

I am trying to fetch information from DHL API but it keeps getting blocked by cors policy.

I have cors policy set up in my backend server, but still, it is causing an error

what am I doing wrong?

this is the error I am getting: "Request header field access-control-allow-methods is not allowed by Access-Control-Allow-Headers in preflight response."

backend:

app.use(cors({
    origin:["http://localhost:3000"],
    method:["GET","POST","OPTIONS","PUT"],
    credentials: true,
    
}));


    app.get("https://api-eu.dhl.com/track/shipments", (req,res) => {
        res.send({msg:ok})
    })

front end:

const trackBtn = () => { 

  
        fetch(`https://api-eu.dhl.com/track/shipments`, {
            method: 'GET',
            params: {trackingNumber: '423432432'},
            headers: {
                'Accept': 'multipart/form-data',
                'DHL-API-Key': 'apF7cO8oD2hN7v',
                'Content-Type' : 'multipart/form-data charset=UTF-8',
                'Access-Control-Allow-Credentials':'*',
                "Access-Control-Allow-Methods":"DELETE, POST, GET, OPTIONS",
                "Access-Control-Allow-Headers":"Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With"
            },
        
            
        }).then(res => {
            console.log(res.data);
        })
        .catch(err => {
            console.log(err);
        });
    }

CodePudding user response：

Remove the Access-Control-Allow-* headers from your request. They belong in the response, that is, are added by the server. You must not include them in a request.

You must also allow the non-standard header DHL-API-Key in your CORS enablement:

app.use(cors({
  origin:["http://localhost:3000"],
  method:["GET","POST","OPTIONS","PUT"],
  credentials: true,
  allowedHeaders: ["DHL-API-Key"]
}));

Lastly, params is not an allowed option for fetch, perhaps you mean

fetch(`https://api-eu.dhl.com/track/shipments?trackingNumber=423432432`, ...)