How to use fetch post json and Sending cookies ?

How are you. I have a question: How to use fetch post json and Sending cookies ? My code:

return fetch('/category/save.json' , {
            credentials: 'include',
            method: 'POST',
            headers: {
                'Accept': 'application/json',
                'Content-Type': 'application/json'
            },
            body: JSON.stringify(data)
        }).then(function(response){
            if (response.status >= 200 && response.status < 300) {
                return response
            } else {
                var error = new Error(response.statusText);
                error.response = response;
                throw error
            }
        }).then(function(response) {
            return response.json();
        }).then(function(json) {
            console.log('parsed json', json)
        }).catch(function(ex) {            
            console.log('parsing failed', ex)
        });

Why cookie not send? Thank you.

[kevin4936]

I only use parameter credentials: ‘include’ , The cookie Can send. But I use parameter credentials: ‘include’ and headers: { ‘Content-Type’: ‘application/json’ } to post json data, Why cookie not send?

[xgqfrms-GitHub]

why & solution

cookie & Fetch & credentials

https://github.com/github/fetch#sending-cookies https://github.com/github/fetch#receiving-cookies