Response status = 0 using fetch polyfill with mode: 'no-cors'

Question

I'm using fetch polyfill with 'no-cors' mode and getting response status 0. In developer tools I can see that response has the requested data.

Client side code:

const BASE_CONFIG = {
    credentials: 'include',
    mode: 'no-cors'
};

let checkStatus = (response) => {
    if (response.status >= 200 && response.status < 300) {
        return response;
    } else {
        var error = new Error(response.statusText);
        error.response = response;
        throw error;
    }
};

function GET(url, urlParams={}, config={}) {
    let requestConfig = {
        method: 'get'
    };
  
    Object.assign(requestConfig, BASE_CONFIG, config);
    return fetch(url, requestConfig)
            .then(checkStatus)
            .then(parseJSON);
}

GET('http://other.domain,{})

Beckend nodejs (Express.js) simplified response handler:

function getData(req, res) {
    var responseData = {data: 'test'};
    res.header("Access-Control-Allow-Origin", "*");
    res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
    res.writeHead(200, {"Content-Type": "application/json"});
    return res.end(JSON.stringify(responseData));
}

Any idea what I'm doing wrong? Thanks!

Answer 1

no-cors mode is only to CDN content, such as scripts, CSS and image, you cannot be used for getting data，response.status = 0 is right behavior

Answer 2

I don't know if you are using file: protocol, but in this case you can get a response status 0.

Neither Chrome's nor Firefox's native implementation supports fetching local files

See : https://github.com/github/fetch/pull/92#issuecomment-140665932

For now, unfortunate as it is, file and ftp URLs are left as an exercise for the reader. When in doubt, return a network error.

See : https://fetch.spec.whatwg.org/#basic-fetch (file and ftp sub sections)