Question

如何使用if ... else if语句继续提示用户提供有效的响应？我的脚本目前只运行一次，但随后中断：

var enterNum = prompt("Please enter a number between 1 and 100", "");


if (isNaN(enterNum)){
    enterNum = prompt("You did not enter a valid number. Please try again", "")
}
else if (enterNum < 1 || enterNum >100){
    enterNum = prompt("Your number is not between 1 and 100. Please try again", "")
}
else{
    document.write("Your number is ", enterNum)
}

提前致谢！

Answer 1

var enterNum = prompt("Please enter a number between 1 and 100", "");

while(isNaN(enterNum) || enterNum < 1 || enterNum >100) {
    enterNum = prompt("You did not enter a valid number. Please try again", "")
}
document.write("Your number is ", enterNum)

Answer 2

你不能只用if / else。使用循环。例如：

var enterNum = prompt("Please enter a number between 1 and 100", "");
while(true)
{
  if (isNaN(enterNum)){
      enterNum = prompt("You did not enter a valid number. Please try again", "")
  }
  else if (enterNum < 1 || enterNum >100){
      enterNum = prompt("Your number is not between 1 and 100. Please try again", "")
  }
  else
    break;
}
document.write("Your number is ", enterNum)

Answer 3

var valid = false;
var msg = "Please enter a number between 1 and 100";

while(!valid){
    var enterNum = prompt(msg, "");

    if (isNaN(enterNum)){
        msg = "You did not enter a valid number. Please try again";
    }
    else if (enterNum < 1 || enterNum >100){
        msg = "Your number is not between 1 and 100. Please try again";
    }
    else{
        valid = true;
        document.write("Your number is ", enterNum)
    }
}

还有很多其他方法可以做类似的事情，有些取决于风格。这是为了便于阅读。也可以消除valid变量，输入正确后只需while(true)然后break。 document.write也可能在一段时间之后。

Answer 4

使用while循环

http://help.dottoro.com/ljqepqhd.php#dowhile

或

http://help.dottoro.com/ljqepqhd.php#while

Answer 5

我讨厌javascript所以我的语法可能已关闭但是类似于：

var isValid = false;
var message = "Please enter a number between 1 and 100";

while(isValid == false)
{
    var enterNum = prompt(message, "");

    if (isNaN(enterNum)){
        isValid = false;
        message = "You did not enter a valid number. Please try again";
    }
    else if (enterNum < 1 || enterNum >100){
        isValid = false;
        message = "Your number is not between 1 and 100. Please try again";
    }
    else{
        isValid = true;
        document.write("Your number is ", enterNum)
    }
}

使用do / while循环可能有点整洁。

在收到有效输入之前，如何继续使用JavaScript if？else if语句？

5 个答案: