How can I detect the distance between 2 entities, in mineflayer?

Question

I am trying to make the bot attack everything it sees, but it gets kicked for trying to hit something out of it's reach, here is my code

var settings = {
    username: 'testingbot',
    host: 'localhost',
    port: 25565,
};

const bot = mineflayer.createBot(settings);

var killer_mode = true;

bot.on("move", () => {
  let friend = bot.nearestEntity();
  if (friend) {
    bot.lookAt(friend.position.offset(0, friend.height, 0));
    bot.setControlState('sprint', killer_mode)
    bot.setControlState('forward', killer_mode)
  }
  if (killer_mode) {
    bot.attack(friend)
  }
});

I tried adding if friend into if (killer_mode), idk what I thought that would do