var randomLoc = Math.floor(Math.random()*5);//Math.floor向下取整，Math.random取0-1之间任意数
var location1 = randomLoc;
var location2 = randomLoc + 1;
var location3 = randomLoc + 2;
var guess;
var hits = 0;
var guesses = 0;
var isSunk = false;

while (isSunk == false) {
    guess = prompt("Ready, aim, fire! (enter a number from 0-6):"); //prompt获取用户输入
    if (guess < 0 || guess > 6) {   //排除法，先排除错误的范围
        alert("Please enter a valid cell number!");
    }else {
        guesses = guesses + 1;
        
        if (guess == location1 || guess == location2 || guess == location3){   // ||或，&&且，！非
           alert("HIT!");
           hits = hits + 1;
           if (hits == 3){
               isSunk = true;
               alert("You sank my battleship!");
           }
     }else {
         alert("MISS");
     }
   }
}
var stats = "You took " + guesses + " guesses to sink the battleship," + " which means your shooting accuracy was " + (3/guesses);
alert(stats);