Help creating javascript choose your own adventure

I was wondering if anyone in the community could help me use javascript to create a choose your own adventure for a project, I was hoping to make it pokemon themed. I have a little bit of it but I was hoping someone could help me add to it. I would myself but I am very new to this and I have no idea how to add more to the possible options and make the game last longer with deeper pathways so far this is what I have


var Chimchar = prompt("You are leaving Twin Leaf Town and you cross a bush with a wild Chimchar, do you FIGHT or RUN ").toUpperCase();

switch (Chimchar) {
case 'FIGHT':
var turtwig = prompt("do you play turtwig, you have a piplup (YES or NO)?").toUpperCase();
var piplup = prompt("you play piplup, hit yes to continue").toUpperCase();
if (turtwig === 'NO' || piplup === 'YES') {
prompt("Piplup uses swim and the chimchar faints, the water move is very effective against the fire type ");
} else {
prompt("Chimchar uses flamethrower and you faint, the fire type move is very effective against your grass type ");
}

break;
case 'CATCH':
var pokeball = prompt("DO you want to throw a pokeball (YES or NO)?").toUpperCase();

if (pokeball === 'YES' ) {
prompt("You throw the pokeball, it rattles for a little bit and then it turns red, showing you that you have caught the pokemon ");
} else {
Prompt("The pokemon runs away ");
}
break;
case 'RUN':
var RUN = prompt("are you sure you want to run (YES or NO)?").toUpperCase();

if (RUN === 'YES' ) {

prompt("You run away suffering no consequences and return to Twin leaf Town ");
}
if (RUN === 'NO' ){
prompt("You continue looking for other pokemon so that you can catch them all");
}

break;
default:
prompt("I didn't understand your choice. Hit Run and try again, this time picking FIGHT, PAY, or RUN!");
}

I would really appreciate any advice or additional code-thanks