Revision 1cd474bc-4cd8-4ffa-aa6d-635dbe7dacd4 - Code Golf Stack Exchange

### Javascript (ES6) <s>50</s> 44 Bytes ###
 a=>a+=[,"st","nd","rd"][a.match`1?.$`]||"th"


###Notes###

 - takes imput as a string
 - Removed 6 bytes, thanks @user81655