如果Javascript中的陳述句條件錯誤

我正在創建一個網站，您可以在其中輸入您的出生時間，代碼會輸出您的年齡（以天為單位）。我通過使用“if”陳述句來實作這一點。我創建了一個用于檢測無效輸入的系統。它會正確檢測無效輸入，但也會將有效輸入檢測為無效。我希望有人能幫我解決這個問題。這是JS代碼。

function ageInDays() {
  // variables
  var birthYear  = prompt("What Year Were You Born In?");
  var ageInDayss = (2021 - birthYear) * 365;

  //text
  if (birthYear > 1990 && birthYear < 2021) {
    var h1         = document.createElement('h1');
    var textAnswer = document.createTextNode("You are "   ageInDayss   " days old.");
    h1.setAttribute('id', 'ageInDays');
    h1.appendChild(textAnswer);
    document.getElementById('flex-box-result').appendChild(h1);
  }

  if (birthYear < 1920 || birthYear != 'NaN' || birthYear > 2021) {
    var h1         = document.createElement('h1');
    var textAnswer = document.createTextNode("Invalid Input. Please Try Again.");
    h1.setAttribute('id', 'ageInDays');
    h1.appendChild(textAnswer);
    document.getElementById('flex-box-result').appendChild(h1);
  }

  if (birthYear > 1920 && birthYear < 1990) {
    var h1         = document.createElement('span');
    var h2         = document.createElement('span');
    var textAnswer = document.createTextNode("You are "   ageInDayss   " days old.");
    var textAnswer1 = document.createTextNode(" Yikes... that's old.");
    h1.setAttribute('id', 'ageInDays');
    h2.setAttribute('id', 'yikes');
    h1.appendChild(textAnswer);
    h2.appendChild(textAnswer1);
    document.getElementById('flex-box-result').appendChild(h1).appendChild(h2);
  }
}

如果您運行此代碼，您可以看到，如果您輸入有效輸入（1920 年到 2021 年之間），它會將輸入檢測為無效。請幫我解決這個問題。

uj5u.com熱心網友回復：

將其包裝在“if”中以首先驗證輸入

 // Age In Days
function ageInDays() {
    // variables
    var birthYear = prompt("What Year Were You Born In?");
    //var ageInDayss = (2021 - birthYear) * 365;
    const bDate  = new Date(birthYear   "-01-01");
    const today = new Date();
    const diffTime = Math.abs(bDate - today);
        const ageInDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24)); 
    // variable css

    //text
if (isNaN(birthYear) == false) {

    
    if (birthYear=>1990 && birthYear<=2021) {
        var h1 = document.createElement('h1');
        var textAnswer = document.createTextNode("You are "   ageInDays   " days old.");
        h1.setAttribute('id', 'ageInDays');
        h1.appendChild(textAnswer);
        document.getElementById('flex-box-result').appendChild(h1);

    } 


    if (birthYear<1990) {
        var h1 = document.createElement('span');
        var h2 = document.createElement('span');
        var textAnswer = document.createTextNode("You are "   ageInDays   " days old.");
        var textAnswer1 = document.createTextNode(" Yikes... that's old.");
        h1.setAttribute('id', 'ageInDays');
        h2.setAttribute('id', 'yikes');
        h1.appendChild(textAnswer);
        h2.appendChild(textAnswer1);
        document.getElementById('flex-box-result').appendChild(h1).appendChild(h2);
    }

 }else{
                var h1 = document.createElement('h1');
        var textAnswer = document.createTextNode("Invalid Input. Please Try Again.");
        h1.setAttribute('id', 'ageInDays');
        h1.appendChild(textAnswer);
        document.getElementById('flex-box-result').appendChild(h1);
 }
}

uj5u.com熱心網友回復：

好吧，你的代碼做了你告訴它做的事情。您正在檢查出生年份是否不是 nan ，顯然不是。你的 if 陳述句應該是這樣的。

if (birthYear < 1990 || birthYear > 2021 || birthYear == "NaN")

標籤：javascript if 语句 输出

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