Calling a API via fetch() - Unexpected end of input

Question

I want to change an API call (external source, no chance to change something on the API side) from PHP to Javascript (Learning purposes).

Because of the cross-origin, I use fetch(). When I run my script, I get an Unexpected end of input error and can't figure out why.

function postData(url = '', data = {}) {
  var headers = new Headers();
  headers.set('Authorization', 'Basic ' + window.btoa("user" + ':' + "pass"));
  return fetch(url, {
    method: 'POST',
    mode: 'no-cors',
    cache: 'no-cache',
    credentials: 'include',
    headers: {
      'Content-Type': 'application/json'
    },
    redirect: 'follow',
    referrer: 'no-referrer',
    body: JSON.stringify(data),
  }).then(response => response.json()).catch(error => console.error(error));
}

postData('https://www.api-endpoint.com/cat1/api/search?', {
  "searchID": "710",
  "isTagged": true
}).then(data => console.log(JSON.stringify(data))).catch(error => console.error(error));

How can I identify the problem with this code? It seems the Authorization is okay. I implemented the search parameters (searchID and isTagged) as described on the manual from the API Dev.

Thanks in advance!

When setting the response. I guess it is because of the empty String as Quentin stated in his answer — youwhatmate
– youwhatmate, Commented Aug 30, 2019 at 12:56

Quentin · Accepted Answer · 2019-08-30 12:52:40Z

4

You said mode: 'no-cors', which disables everything which requires CORS permission.

Since reading data across origins requires CORS permission, there is no data.

Trying to parse an empty string as JSON results in the unexpected end of input because the input ended before there was any JSON.

(Note that other things which require CORS permissions, and which you are trying to do, include setting the content-type to JSON and including credentials).

answered Aug 30, 2019 at 12:52

Quentin

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10 Comments

Quentin Over a year ago

@youwhatmate — So the server isn't using CORS to grant you permission. stackoverflow.com/a/35553666/19068

MarcoS Over a year ago

You can't fetch data across origins without CORS. You definitely need a proxy on your same origin.

Quentin Over a year ago

"I tried the browser extension" — The answer I pointed you to says: "They also tend to work only with simple requests (failing when handling preflight OPTIONS requests).". Since you are doing plenty of stuff that needs a preflight, that is to be expected.

Quentin Over a year ago

"jsonp" — Which says "Bob could also provide the data using a hack like JSONP" … did you ask if the API you were using supported JSONP? And since you can't (a) make a POST request (b) set credentials or (c) set headers with JSONP … it wouldn't be remotely equivalent anyway.

Quentin Over a year ago

"the other solution" — Which other solution? The proxy? Not writing a web app? Talking to the people running the service you are trying to POST to?

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