嗨，我是 javascript 新手。
我正在尝试实现一些 javascript 表单验证我正在尝试使用此处使用的技术： http ://www.w3schools.com/js/tryit.asp?filename=tryjs_form_validation ://www.w3schools.com/js/tryit.asp?filename=tryjs_form_validation 来测试表单中的空字段并使用警报警告用户但这对我不起作用当我提交一个空表单时继续到 jsp 文件并且 javascript 没有捕获错误
这是表单所在的 index.html 文件
<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>'
有没有人看到我做错了什么。谢谢你的时间。