Revision 36f3c06d-abfb-46d9-816c-ad3161fd8465 - Code Golf Stack Exchange

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


### Notes ###

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