Javascript Basic If Else not working

e.g.

confirm("You ready to play this @#$%, dawg!?");

var age = prompt("What's your age?");

if(age > 13) {

console.log("You can play but we will not take any responsibility!");

}
else {

console.log("Play on!");

}

console.log("You are at a Justin Bieber concert, and you hear this lyric 'Lace my shoes off, start racing.'");

console.log("Suddenly, Bieber stops and says, 'Who wants to race me?'");

var userAnswer = prompt("Do you want to race Bieber on the stage?"); 

if (userAnswer = "yes") 

{

console.log("You and Bieber start racing. It's neck and neck! You win by a shoelace!");

}

else {

console.log("Oh no! Bieber shakes his head and sings 'I set a pace, so I can race without pacing.'")
}

Even if you say no or anything else besides yes, the answer will still be : You and Bieber start racing. It's neck and neck! You win by a shoelace!