如何在输入想要的值之前每次都显示提示符

Question

这是一个简单的JS示例，我正在尝试“改进”它。

我是一个JS完全初学者，我希望我不会介入我的头在这里。

var color1 = prompt("Enter first color: yellow, red or blue");
var color2 = prompt("Enter second color: yellow, red or blue"); 

if (color1 == "yellow" && color2 == "yellow"){
      console.log("mixing of these two colors makes yellow");
    }
if (color1 == "red" && color2 == "red"){
      console.log("mixing of these two colors makes red");
    }
if (color1 == "blue" && color2 == "blue"){
      console.log("mixing of these two colors makes blue");
    }
if (color1 == "yellow" && color2 == "red" || color1 == "red" && color2 == "yellow"){
      console.log("mixing of these two colors makes orange");
    }
if (color1 == "yellow" && color2 == "blue" || color1 == "blue" && color2 == "yellow"){
      console.log("mixing of these two colors makes green");
    }
if (color1 == "blue" && color2 == "red" || color1 == "red" && color2 == "blue"){
      console.log("mixing of these two colors makes purple");
    }

我要做的是不允许第二个提示符出现，直到正确地输入第一个提示符(即:黄色、红色、蓝色)，不管用户输入“错误”值多少次。

我知道我必须用“时间”，但我不知道怎么用。用不同的方法尝试了几次，但没有得到想要的结果。

也尝试了一些有类似问题的线程，但是找不到解决这个具体问题的方法。

任何帮助或建议都是非常欢迎的。

谢谢。

Answer 1

使用shown循环，如下所示

var colors = ["red","yellow","blue"];
var color1 = prompt("Enter first color: yellow, red or blue");
while(colors.indexOf(color1)==-1){
    color1 = prompt("Enter first color: yellow, red or blue");
}
var color2 = prompt("Enter second color: yellow, red or blue"); 

Answer 2

试试这个：

var valid_colors = ['yellow', 'red', 'blue'];
var color1;
var color2;

color1 = prompt("Enter first color: yellow, red or blue");

while (!~valid_colors.indexOf(color1)) {
    color1 = prompt("Enter first color: yellow, red or blue");
}

color2 = prompt("Enter second color: yellow, red or blue"); 

while (!~valid_colors.indexOf(color2)) {
    color2 = prompt("Enter second color: yellow, red or blue");
}

//... continue with your code

Answer 3

我会这样做：

var allowedColors = ['yellow', 'red', 'blue']; //we create array of valid input

var color1 = ''; // initial value is not correct, so user is prompted at least once.

var color2 = '';

while(allowedColors.indexOf(color1) === -1){

    color1 = prompt("Enter first color: yellow, red or blue");

}

while(allowedColors.indexOf(color2) === -1){

    color2 = prompt("Enter second color: yellow, red or blue"); 

}