nginx奇奇怪怪的跨域问题，报错“Response to preflight request doesn't pass access control check: It does not have HTTP ok status”

location / {
......
if ($request_method = OPTIONS ) {
    add_header Access-Control-Allow-Origin "*";
    add_header Access-Control-Allow-Methods "POST, GET, PUT, OPTIONS, DELETE";
    add_header Access-Control-Max-Age "3600";
    add_header Access-Control-Allow-Headers "Origin, X-Requested-With, Content-Type, Accept, Authorization";
    add_header Access-Control-Allow-Credentials "true";
    add_header Content-Length 0;
    add_header Content-Type text/plain;
    return 200;
}
......
nginx -t && nginx -s reload