使用jsp调用javascript函数时出现问题

Question

<form name='frm' action="Readcsvv" enctype="multipart/form-data" method="POST" > 
<input type="file" name="file1"><br><br>
<input type="Submit" value="Upload File" onclick="showProgress()" method="POST">

<script>
function showProgress() {
    if(document.frm.file1.value == "")
    {
    alert('Please upload a file');
    }       
    else
    {       
    document.getElementById('progress').style.display = 'block';
    }
    }
</script>

In my jsp file I have the above code. If there is no file selected the alert('Please upload a file') is displayed successfully . But it calls the servlet program Readcsvv and goes to the next page.

After diplaying the alert box i want to program to be in same page. What should I do for that?

Answer 1

<input type="Submit" value="Upload File" onclick="return showProgress()" method="POST">

将其与return false一起使用

Answer 2

If this were jQuery you would have to return false at the end of an onClick event handler. I would try return false; .

You also need to change your onclick attribute to be an onsubmit attribute on the form element.

Answer 3

尝试这个：

<form name='frm' action="Readcsvv" enctype="multipart/form-data" method="POST" onSubmit="return false;"> 

Answer 4

Try below,

<form name='frm' action="Readcsvv" enctype="multipart/form-data" method="POST" > 
<input type="file" name="file1"><br><br>
<input type="Submit" value="Upload File" onclick="return showProgress();" method="POST">

<script>
function showProgress() {
    if(document.frm.file1.value == "")
    {
    alert('Please upload a file');
    return false;
    }       
    else
    {       
    document.getElementById('progress').style.display = 'block';
    return true;
    }
    }
</script>