Agregar operador en JavaScript

number => 2+3=5 (integer)
string => contact to string "good"+"morning"="goodmorning" (string)
string + number => 2+"hello"="2hello" (string)

but => 
var name="sara" , age=18 , num=22 

name+age+num => "sara1822"
age+num+name => "40sara"
zizi-engi