javascript空字段表單驗證不起作用

Question

嗨，我是javascript新手。

我正在嘗試實現一些JavaScript表單驗證，我正在嘗試使用此處使用的技術： http : //www.w3schools.com/js/tryit.asp?filename=tryjs_form_validation以測試表單中的空字段並使用警報向用戶發出警告，但對我來說不起作用當我向jsp文件提交空表單時，javascript無法捕獲錯誤

這是我的index.html文件，其中的表單是

<html>
  <body>
    <head>
    <script>
        function validateForm()
        {
            var stoneField=document.forms["bmiForm"]["stone"].value;
            var poundsField=document.forms["bmiForm"]["pounds"].value;
            var kgsField=document.forms["bmiForm"]["kgs"].value;
            var feetField=document.forms["bmiForm"]["feet"].value;
            var inchesField=document.forms["bmiForm"]["inches"].value;

            if ( stoneField = null || stoneField = "" && poundsField = null || poundsField = "" && kgsField = null || kgsField = "" && feetField = null || feetField = "" && inchesField = null || inchesField = "" )
            {
              alert("Please enter a weight and height");
              return false;
            }
            else
            {

             return true;
            } 
        }
    </script>
</head>
<form name ="bmiForm" action="PrintBMI.jsp" onsubmit="return validateForm()" method=post  style="width:250px;">
    <fieldset>
    <legend>BMI Calculator</legend>
    <h3>Enter your weight</h3>
    Stone <input type = text name = "stone" size = 1 maxlength = 2>
    Pounds <input type = text name = "pounds" size = 1 maxlength = 2>
    <br>
    <strong>OR</strong>
    <br>
    KGs <input type = text name = "kgs" size = 1 maxlength = 3>

    <h3>Enter your height</h3>
    Feet <input type = text name = "feet" size = 1 maxlength = 1>
    Inches <input type = text name = "inches" size = 1 maxlength = 2>
    <br>
    <strong>OR</strong>
    <br>
    Metres <input type = text name = "metres" size = 1 maxlength = 4>
    <p><input type=submit value = "Get BMI">
    </fieldset>
</form>
</body>
</html>'

有人看到我在做什么錯嗎？ 謝謝你的時間。

Answer 1

在此代碼中將=替換為=== ：

if ( stoneField = null || stoneField = "" && poundsField = null || poundsField = "" && kgsField = null || kgsField = "" && feetField = null || feetField = "" && inchesField = null || inchesField = "" )

了解比較運算符

Answer 2

if ( stoneField = null || stoneField = "" && poundsField = null || poundsField = "" && kgsField = null || kgsField = "" && feetField = null || feetField = "" && inchesField = null || inchesField = "" )
        {
          alert("Please enter a weight and height");
          return false;
        }

如果不是，請在===內部使用=

Answer 3

USE ==用於比較值。

在代碼中替換下面的代碼塊。

if ( stoneField == null || stoneField == "" && poundsField == null || poundsField == "" && kgsField == null || kgsField == "" && feetField == null || feetField == "" && inchesField == null || inchesField == "" )

javascript空字段表單驗證不起作用

問題描述

3 個解決方案

解決方案1
1 已采納 2013-01-31 10:57:26

解決方案2
0 2013-01-31 10:58:12

解決方案3
0 2013-01-31 11:00:31

javascript空字段表單驗證不起作用

問題描述

3 個解決方案

解決方案1 1 已采納 2013-01-31 10:57:26

解決方案2 0 2013-01-31 10:58:12

解決方案3 0 2013-01-31 11:00:31

解決方案1
1 已采納 2013-01-31 10:57:26

解決方案2
0 2013-01-31 10:58:12

解決方案3
0 2013-01-31 11:00:31