Fetch: post json data, application/json change to text/plain

Question

I'm using chrome 53.0.2785.116 m (64-bit).

I got the following headers on devtools. The problem is marked with a "//" comment. content type is really not allowing us to set it to application/json, I have tried a 100 different ways.

import fetch from 'isomorphic-fetch'; const option = {     method: 'POST',     mode: 'no-cors',     headers: {       'Accept': 'application/json',       'Content-Type': 'application/json'     },     body: JSON.stringify({'aa':'bb'}) } fetch('/books', opts) .then(check401) .then(check404) .then(jsonParse) .then(errorMessageParse); 

Request Headers

accept:application/json Accept-Encoding:gzip, deflate Accept-Language:zh-CN,zh;q=0.8 Connection:keep-alive Content-Length:97 content-type:text/plain;charset=UTF-8 //What happen? Host:127.0.0.1:8989 Origin:http://127.0.0.1:8989 Referer:http://127.0.0.1:8989/ User-Agent:Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36 

Answer 1

The problem is that when you work in 'mode' 'no-cors', the Headers become an immutable and you will not be able to change some of its entries. One of the heads you can't change is the Content-Type. When you set 'mode' to 'no-cors' you will be able to change only these headers:

• Accept
• Accept-Language
• Content-Language
• Content-Type and whose value, once parsed, has a MIME type (ignoring parameters) that is application/x-www-form-urlencoded, multipart/form-data, or text/plain

In another words, in 'mode' '-no-'cors' you can only set application/x-www-form-urlencoded, multipart/form-data, or text/plain to the Content-Type.

So the solution is stop using fetch or changing it to 'cors' 'mode'. Of course this will only works if your server also accepts 'cors' requests.

Here is an example of how you could enable CORS in an Apache Server

SetEnvIfNoCase Access-Control-Request-Method "(GET|POST|PUT|DELETE|OPTIONS)" IsPreflight=1 SetEnvIfNoCase Origin ".*" AccessControlAllowOrigin=$0 SetEnvIfNoCase Origin "https://(url1.com|url2.com)$" AccessControlAllowOrigin=$0  Header always set Access-Control-Allow-Origin %{AccessControlAllowOrigin}e env=AccessControlAllowOrigin Header always set Access-Control-Allow-Methods "GET, POST, PUT, DELETE, OPTIONS" env=IsPreflight Header always set Access-Control-Allow-Headers "Content-Type, Authorization, Accept, Accept-Language" env=IsPreflight Header always set Access-Control-Max-Age "7200" env=IsPreflight RewriteCond %{REQUEST_METHOD} OPTIONS RewriteCond %{ENV:IsPreflight} 1 RewriteRule ^(.*)$ $1 [R=204,L] 

The above code will inject the CORS headers in the response when its necessary. With this code your server will allow CORS only from the the domains "url1.com" or "url2.com".

Here are some references

• https://developer.mozilla.org/en-US/docs/Web/API/Request/mode
• https://fetch.spec.whatwg.org/#simple-header