SyntaxError: Unexpected token if

im currently learning javascript and i keep having this error!!!

This is my script:

var compare = function(choice1, choice2)

if (choice1 === choice2) { return "The result is a tie!"; }

else if (choice1 === "rock")

if (choice2 === "scissors") { return "rock wins"; }

else  {
    return "paper wins";  }