Number guessing game

Number guessing game. Pure JavaScript.
Code:

alert("Instructions: Guess a number 1 through 100. If you want to leave, type \'stop\'.");
var condition = "Guess a number 1 through 100. Type \'stop\' to leave.";
var User = "???";
var i = Math.ceil(Math.random() * 100);
var num = 0;
while(true){
    User = prompt(condition);
    if(User.includes("stop")){
       break; 
    }
    num = Number(User);
    if(num > i){
        condition = "Try to guess lower. Guess a number 1 through 100. Type \'stop\' to leave.";
    }
    if(num < i){
        condition = "Try to guess higher. Guess a number 1 through 100. Type \'stop\' to leave.";
    }
    if(num == i){
        alert("Great! You guessed right!");
        break;
    }
}