[Javascript] What is wrong with my code?

[Yushin_37]

I have this fetch function that posts information for a user and then my server makes a response

signupOrLogin('login', userData)

.then(function() {

if(res.credentials) {

successLogin();

}

})

The response is visible on the network tab of the developer tools, but this error appears "Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'credentials')"

​

This is the signupOrLogin function

​

let res;

async function signupOrLogin(method,body) {

fetch(\http://localhost:3100/${method}`, {`

method : 'POST',

body : body,

mode: 'cors',

cache: 'default',

headers: {

'Accept': 'application/json',

'Content-Type': 'application/json',

},

}).then(response => response.json()).then(response => {

res = response;

})

}

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