Question

您好我是javascript的新手。

我正在尝试实现一些javascript表单验证我试图使用这里使用的技术： http://www.w3schools.com/js/tryit.asp?filename=tryjs_form_validation 测试表单中的空字段并使用警报来警告用户但它对我不起作用当我提交一个空表单继续jsp文件并且javascript没有捕获错误

这是我的index.html文件，表单是

<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>'

有谁看到我做错了什么。谢谢你的时间。

Answer 1

在此代码中将=替换为===：

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

了解Comparison Operators

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;
        }

使用=== inside if，not =

Answer 3

USE ==用于比较价值。

替换代码中的下面的代码块。

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

javascript空字段表单验证无效

3 个答案: