for me not happening same code , am getting error function jjj(asi) { var mno = 4 *asi; return mno; } console.log(jjj(12)); console.log(mno); vendor.798982f3e65c434662d8.bundle.js:1 48 VM671:6 Uncaught ReferenceError: mno is not defined at <anonymous>:6:13

you can use 304 as not modified if you have any doubt in status code just check here or feel free to ask http://www.restapitutorial.com/httpstatuscodes.html