Fetch returns nothing

Question

I'm doing an API with aws lambda and API gateway, but when I make a request with fetch it returns nothing and gives me "No 'Access-Control-Allow-Origin' header is present on the requested resource" message

I tried to use curl and other website to do this request and the answer was

{"statusCode":200,"headers":{"Access-Control-Allow-Origin":"*","Access-Control-Allow-Methods":"POST"},"body":"oi"}

And that is what I expected, but using fetch in a js code it returns me the error: "No 'Access-Control-Allow-Origin' header is present on the requested resource"

And Access-Control-Allow-Origin is already in header of response

The lambda code:

    callback(null, {
        statusCode: 200,
        headers: {
            "Access-Control-Allow-Origin":"*",
            "Access-Control-Allow-Methods":"POST"
        },
        body: "oi"
    })
}

The fetch code:

fetch('URL', {
    method: 'POST',
})
.then((oi) => oi.json())
.then((json) => console.log(json))

Possible duplicate of [Why does my JavaScript code get a "No 'Access-Control-Allow-Origin' header is present on the requested resource" error when Postman does not?](https://stackoverflow.com/questions/20035101/why-does-my-javascript-code-get-a-no-access-control-allow-origin-header-is-pr) — Dan Starns, Oct 10 '19 at 19:10
I don't think it's a duplicate because i already have Access-Control-Allow-Origin: * in my response header — Paulo Mesquita, Oct 10 '19 at 19:20
Possible duplicate https://stackoverflow.com/questions/35190615/api-gateway-cors-no-access-control-allow-origin-header — BFunk, Oct 10 '19 at 20:05
I tried that solutions and nothing worked, and with curl works, so I think maybe is a problem with the way I did my fetch request, but I don't know what is it — Paulo Mesquita, Oct 11 '19 at 03:51

score 1 · Accepted Answer · answered Oct 11 '19 at 04:08

1

I solve the problem going in aws console in API gateway and setting the headers there instead of just in the code

answered Oct 11 '19 at 04:08

Paulo Mesquita

103
8

Please, could you check it as the preferred answer in order for others to know it is already solved? – Ictus Jun 29 '20 at 04:06

score 0 · Answer 2 · answered Oct 10 '19 at 19:15

0

Without more information this is hard to diagnose, but I would assume you need to enable CORS on your AWS lambda function. Without seeing some of the lambda code its hard to give you any help.

answered Oct 10 '19 at 19:15

BFunk

387
5
11

I did just a test code `exports.handler = function(event, context, callback){ callback(null, { statusCode: 200, headers: { "Access-Control-Allow-Origin":"*", "Access-Control-Allow-Methods":"POST" }, body: "oi" }) }` – Paulo Mesquita Oct 10 '19 at 19:21
What is the trigger for your lambda? – BFunk Oct 10 '19 at 19:31
I use API gateway to call it with a request – Paulo Mesquita Oct 10 '19 at 19:34
Follow this documentation to make sure that CORS is allowed on the API Gateway https://docs.aws.amazon.com/apigateway/latest/developerguide/how-to-cors.html – BFunk Oct 10 '19 at 19:35
I did this all, enable cors in API gateway and put the headers in the response the problem of this is when I use a sniffer to see the return, the function do not return me nothing – Paulo Mesquita Oct 10 '19 at 19:50
I'm not sure what you mean by sniffer. Have you tried the same request using curl or an app like Postman? – BFunk Oct 10 '19 at 20:01
CORS always seems to be a headache. I setup a test lambda and enabled cors and it seems to work for me I did notice that I had to enable CORS on the resource itself. not just the method. Also, your lambda is allowing CORS on a POST request but your fetch is making a GET request – BFunk Oct 11 '19 at 04:56

Fetch returns nothing

2 Answers2