使用javascript在jsp中显示错误消息

Question

I have a jsp file contains a form and I need to validate the form. The jsp page will be opened as pop-up page and hence I choose not to pop-up the validation message again. Here is my code.

<script type="text/javascript"> 
    function validateForm() {
        var x=document.forms["myForm"]["name1"].value;
        if (x.trim().length<=4){
            return false;
        }
    }
</script>

<form name="myForm" method="POST" action="write.jsp" onsubmit="return validateForm();">
    Name: <input type="text" name="name1" value="<%=name%>" size="20"/>  <br> 
    Price: <input type="text" name="price"  value="<%=price%>" size="20" /><br> 
    Due time: <input type="text" name="DueTime"  value="<%=dueday%>" size="20" /><br> 
    Location: <input type="text" name="Location"  value="<%=address%>" size="20" /><br> 
    Photo Url: <input type="text" name="url"  value="<%=imagePath%>" size="20" /><br> 
    Description: <input type="text" name="desc"  value="<%=desc%>" size="20" /><br> 
    <input type="submit" name="submit" onclick="window.close()"/>
    <% if(validateForm = false) { %> <a>error message</a> <% } %>
</form>

I am validating for first input "name1" only and the input length is less than 4.
I'd like to display a error message below the submit button. The codes is not working, can anyone help me to fix this?

Answer 1

Use document.getElementsByName("name1") instead of document.forms["myForm"]["name1"].value;

Use as

function validateForm()
{
var x=document.getElementsByName("name1").value;
if (x.trim().length<=4)
  {
    alert("Message");
    return false;
  }
}

Answer 2

 document.getElementsByName('name1')[0].value;  

in place of

document.forms["myForm"]["name1"].value;

---

use a span below the submit button
html

<span id="error"></span>

script

function validateForm()
                {
                var x=document.getElementsByName('name1')[0].value;
                if (x.trim().length<=4)
                  {
                    document.getElementById("error").innerHTML="atleast 4 letters required in name";
                    return false;
                  }
                }