Two requests.. different handling by rails

Controller.rb

def upload_images
  	render :js => "alert('Hello Rails');"
end

DropzoneJsAjaxRequest

--- Request Header ----

POST /texts/82/upload_images HTTP/1.1
Host: localhost:3000
Connection: keep-alive
Content-Length: 40004
Pragma: no-cache
Cache-Control: no-cache
Origin: http://localhost:3000
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/43.0.2357.65 Safari/537.36
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryTBlcIVEmNGYd8Dxx
Accept: application/javascript, */*;q=0.5, text/javascript, application/ecmascript, application/x-ecmascript
X-Requested-With: XMLHttpRequest
Referer: http://localhost:3000/texts/82
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.8
Cookie: locale=en; __profilin=p%3Dt; request_method=POST; _xyz-tool_session=dzRPT3NwblFmRFpiaCsyZlo2VEZwNXc4Z3h6Z3hDdjZGTlVVSlI1WmMxWUduUmVweWJ2RzEzNkpraDJjQmlRRUp3MGo2UGEweUNJS1lUdTlkQmx1Q1NhT1NpN1ozTlJDbWxYamM5bGtkRDVMcWlYUys4VGN3dG1pNFkzZm9YL1VUSWhwQVhqZk5YVUE0UXV4Q2FWSE9SeXJKRmVpeFkyN0VuUUZublBaR3JFQWU0aDNaUVlBbmFGU005V2ZqODE0dWZVdzhhd1ZBQXVRMEFCYkFnSnBFVk9qZlNObkxRd2grQmpKQ3pqdVFhdDlUcTFPUlhIOFd0YXZDL2dMaGE2MHArVVIvbERrbjZkSUF5V2w1eGE1RkE9PS0taUxSSXArRkZqalpxdmN5WnFRbGhMQT09--5bb793495216237abe559233508d9fe41be51563

--- Response Header --

HTTP/1.1 200 OK
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
X-UA-Compatible: chrome=1
Content-Type: text/javascript; charset=utf-8
ETag: "2e4c62eb69308d42e72bb24e9eee7a04"
Cache-Control: max-age=0, private, must-revalidate
Set-Cookie: _xyz-tool_session=UzN2VEFVS1lJSFlIUHN5eDd3RFl0SzhzMWk2WHI2alhNalMyemF2U1JhZWZEU3pmUEhXaXIrNENoQXRvQUwyS0s3Q1RKMm9BSlk5Rzg0RVhqOTlHWDIvcjBDVjhxTTlpWlNyWTVFQXVSZWh6Y2JoVlJrT0hQdzIwcVJUU094QWphVzR4TXNuYXBvSkxaMmg1L2I5dFZoVGQwVm13YjlJWFRndlNyY0Q1VUEyZVk5WUVBSEN3Vkd3b2FSdFlnMWdBTGo4bjg1ZGRUZk5xRndPTGxzL2RBaURiL0xIWUtaa3M0d2hCZGMrSjIzeWhsMUhhRkFNTkpBRGFDdmw5b1Q5UDUweENkWWVMVERwRDNUTTF3VEkrbGc9PS0tZUYxTXl6UzRMaGtENEthUzVsTlNhUT09--a03dae7271f8c4def3ac01fd66aebd1be1571339; path=/; HttpOnly
X-Request-Id: 9e78225e-49bd-446b-b590-b1f02030a1c1
X-Runtime: 15.042383
Connection: close
Server: thin 1.6.1 codename Death Proof

jqueryAjaxrequest

--- REQUEST HEADER ---

POST /texts/82/upload_images HTTP/1.1
Host: localhost:3000
Connection: keep-alive
Content-Length: 32
Pragma: no-cache
Cache-Control: no-cache
Origin: http://localhost:3000
X-CSRF-Token: VlgCe5g9Ic3XgwL+HF/tPRAVZnlKJ97Fb5ZkgVsYlPM=
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/43.0.2357.65 Safari/537.36
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Accept: */*;q=0.5, text/javascript, application/javascript, application/ecmascript, application/x-ecmascript
X-Requested-With: XMLHttpRequest
Referer: http://localhost:3000/texts/82
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.8
Cookie: locale=en; __profilin=p%3Dt; request_method=POST; _xyz-tool_session=UzN2VEFVS1lJSFlIUHN5eDd3RFl0SzhzMWk2WHI2alhNalMyemF2U1JhZWZEU3pmUEhXaXIrNENoQXRvQUwyS0s3Q1RKMm9BSlk5Rzg0RVhqOTlHWDIvcjBDVjhxTTlpWlNyWTVFQXVSZWh6Y2JoVlJrT0hQdzIwcVJUU094QWphVzR4TXNuYXBvSkxaMmg1L2I5dFZoVGQwVm13YjlJWFRndlNyY0Q1VUEyZVk5WUVBSEN3Vkd3b2FSdFlnMWdBTGo4bjg1ZGRUZk5xRndPTGxzL2RBaURiL0xIWUtaa3M0d2hCZGMrSjIzeWhsMUhhRkFNTkpBRGFDdmw5b1Q5UDUweENkWWVMVERwRDNUTTF3VEkrbGc9PS0tZUYxTXl6UzRMaGtENEthUzVsTlNhUT09--a03dae7271f8c4def3ac01fd66aebd1be1571339

--- RESPONSE HEADER ----

HTTP/1.1 200 OK
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
X-UA-Compatible: chrome=1
Content-Type: text/javascript; charset=utf-8
ETag: "2e4c62eb69308d42e72bb24e9eee7a04"
Cache-Control: max-age=0, private, must-revalidate
Set-Cookie: _xyz-tool_session=WGVMdk5GdDVhVloxVmFtLzhZdmRmQmN4amowOXJEZGVLM1lzQ01NR3plTWJlQ1M4QVpSR3U3eFpnUGhrWnZhTHlVbTIxa091Q2cydnlLaTVqL1BtazAyRTFJN0pXTy9jRENnMld2ZFk1cDAvM0x5OUxabWVJQ2ljMUV6TjR6V3g1dk93a3p6b1IybFcwQTdCcENqSlRXdmR0dCtVVHd2ck9DUUk4WTdVbStqVXF6dUxqaStzNUlZNHFXZW1DemVONjVIcTVZTmVMM3hkdFc1WWdVSFh5eWtTMmdpM2NmTTkvRUZUT1Ntb2V2TTVyYW9Wb0hCVWZ1eHFKWlhmV3dNWHlGVmUwaWwvRGxiMDBGcW9lUzNGV3c9PS0tR2tPN3dlNUlPbFdMSDlVUDd2V2NxUT09--9eca610531964860418b8d849b93e75d232c3eaf; path=/; HttpOnly
X-Request-Id: 29c600ea-4567-45ca-ac8a-c2f222642fcb
X-Runtime: 0.474763
Connection: close
Server: thin 1.6.1 codename Death Proof