javascript - 无法检查空字符串和 null 的提示

Question

这是我的代码:

    let guessTheNumber = () => {
        let randomNumber = Math.round((Math.random()) * 10); //generating a random number from 1 to 10
        console.log(randomNumber); //added this just to see what number was generated
        let question = +prompt('Please, try to guess the number from 1 to 10!'); // by using unary plus I want prompt to return a number, NOT a string
        if (question === randomNumber) {
            alert('Wow, you are quite lucky. Nice job!'); //this one works 
        }
        else if (question !== randomNumber) {
            alert('Nope'); //this one is also easy to check
        }
        else if (question === "") {
            alert('You did not enter anything!'); 
        }
        else {
            alert('Why did you cancel?');
        }
    }
    guessTheNumber();

当question等于randomNumber变量时，我可以成功检查它。但是，当我尝试提醒某些内容时，如果存在空字符串(单击“确定”而不输入任何内容)或 null(单击“取消”)，则程序将失败。

Answer 1

提示符之前的(+)将 convert the response to a Number因此，如果用户取消或将提示留空，它将始终返回 0

因此，如果您需要检查取消，则需要删除(+)，然后提示将返回一个字符串 或 null，因此您需要一些额外的逻辑。

let guessTheNumber = () => {
  // using 'Math.ceil' as @symlink mentioned
  let randomNumber = Math.ceil((Math.random()) * 10);
  console.log(randomNumber);
  let question = prompt('Please, try to guess the number from 1 to 10!');

  // check for cancel 'null'
  if (question == null) {
    alert('Why did you cancel?');
    // you need to exit so it won't prompt again
    return
  }
  // parseInt() function parses a string argument and returns an integer
  else if (parseInt(question, 10) === randomNumber) {
    alert('Wow, you are quite lucky. Nice job!');
  }
  // empty value
  else if (question === '') {
    alert('You did not enter anything!');
    // run again
    guessTheNumber();
  }
  // not a number
  else if (isNaN(question)) {
    alert('Please enter a number');
    // run again
    guessTheNumber();
  }
  // wrong answer
  else {
    alert('Nope!')
    // run again
    guessTheNumber();
  }
}
guessTheNumber();