No 'Access-Control-Allow-Origin' AWS Lambda - node.js

Question

happy new year everybody!
So I have a reactJS API call which looks like this:
async function callApi() {
const requestData = {
headers: {
Authorization: token
}
}
if (calledAPI === false) {
let data = await API
.get('caresyncauthapi' , '/access', requestData)
.then(response => {
let arr = {};
arr = response.Items;
setZorgSearchData(arr)
})
}
calledAPI = true;
}
The Lambda it calls looks like this:
exports.handler = async (event) => {
if (event.requestContext.authorizer) {
const claims = event.requestContext.authorizer.claims;
username = claims['cognito:username'];
}
var params = {
TableName: tableName,
IndexName: "ZorgverlenerID-index",
KeyConditionExpression: "#ZorgverlenerID = :zorg_id",
ExpressionAttributeNames: {
"#ZorgverlenerID": "ZorgverlenerID"
},
ExpressionAttributeValues: {
":zorg_id": username
}
};
try {
data = await dynamodb.query(params).promise();
console.log( "Status code : 200");
console.log(data.Items);
let response =
{
statusCode: 200,
headers: {
'Access-Control-Allow-Origin': '*',
'Access-Control-Allow-Headers': '*',
},
body: JSON.stringify(data.Items)
}
return JSON.stringify(response);
} catch (error){
console.log( "Status code : 400, Error code : ", error.stack);
}
};
Basically the Lambda gets the context from the sent token (username of the person logged in).
It then queries this database with this username, it then puts the result in a json and returns it.
The await dynamodb.query(params).promise(); gives me an 200 (success) and it also prints the correct data I want to return in cloudwatch.
But when the data returns to my ReactJS application i recieve:
Access to XMLHttpRequest at 'https://qcesrr2td3.execute-api.eu-west-1.amazonaws.com/devl/access' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
xhr.js:187 GET https://qcesrr2td3.execute-api.eu-west-1.amazonaws.com/devl/access net::ERR_FAILED 502
dispatchXhrRequest # xhr.js:187
xhrAdapter # xhr.js:13
Thing I already tried:
Enabling CORS in the API gateway
Changing up the headers in the response
Returning the response without JSON.stringify, its null then
Does anybody have an idea what I can still change?

Answer 1

Fixed it by not stringifying my response:
try {
data = await dynamodb.query(params).promise();
console.log( "Status code : 200");
console.log(data.Items);
let response =
{
statusCode: 200,
headers: {
"Access-Control-Allow-Headers": "*",
"Access-Control-Allow-Origin": "*",
"Access-Control-Allow-Methods" : "OPTIONS,POST,GET,PUT"
},
body: JSON.stringify(data)
}
return response;
} catch (error){
console.log( "Status code : 400, Error code : ", error.stack);
}
Weird because this code worked for a week then suddenly stopped. Oh well it works again.