JavaScript 无效输入条件

Question

我是 JavaScript 新手。前几天我做了一个剪刀石头布的游戏。游戏运行良好，但我想知道你能否提出一个条件，如果用户选择输入无效的选择，则会出现一个警告框，然后说输入无效之类的!这是我的代码!

   var userchoice=prompt("Wanna play Rock, Paper and Scissors?");{
    if (userchoice!="paper") {
        alert("Invalid ID");
    }
    else if (userchoice!="scissors") {
        alert("Invalid ID");
    }
    else (userchoice!="rock") {
        alert("Invalid ID");
    }
}
var computerchoice=Math.random();{
    if(computerchoice<0.34){
    console.log(computerchoice="paper");
    }
    else if (computerchoice<=0.67) {
        console.log(computerchoice="rock");
    }
    else{
        console.log(computerchoice="scissors");
    }
};
var compare=function(choice1,choice2){
    if (choice1===choice2){
        console.log("The game was a tie!");
    }
    else if (choice1==="rock") {
        if (choice2==="scissors") {
            console.log("rock wins!");
        }
        else{
            console.log("paper wins!")
        }   
    }
    else if(choice1==="paper"){
        if (choice2==="rock") {
            console.log("paper wins!");
        }
        else{
            console.log("scissors wins!");
        }
    }
    else if (choice1==="scissors") {
        if (choice2==="paper") {
            console.log("scissors wins!")
        }
        else {
            console.log("rock wins!");
        }
    }
};

compare(userchoice,computerchoice);
console.log("User: "+userchoice);
console.log("Computer: "+computerchoice);
//End of Game

Answer 1

这里有一些压缩代码，用于确定是否有任何选择无效。如果有无效的选择，它会发出警报，但您应该将其更改为更合适的行为。

var VALID_CHOICES = ['rock', 'paper', 'scissors']
var choice1 = 'rock', choice2 = 'something invalid'
var invalidChoice = false
;[choice1, choice2].forEach(function(choice) {
  if (VALID_CHOICES.indexOf(choice) === -1) invalidChoice = true
})
if (invalidChoice) alert('Picked an invalid choice')