How to create case using Sforce connection

You forgot to add JS files for AJAX toolkit, which is why you are facing sforce connect. Add belowscript and session Id (If you are inserting records in the same org no need to use username password.)

     sforce.connection.sessionId = '{!$Api.Session_ID}';   

If you want to create any record then use it like this..

In this example I am creating Account record

        sforce.connection.sessionId = '{!$Api.Session_ID}';   function test() { var account = new sforce.SObject("Account"); account.Name = "my new account"; var result = sforce.connection.create([account]); if (result[0].getBoolean("success")) { log("new account created with id " + result[0].id); } else { log("failed to create account " + result[0]); } }