javascript - How to block form submit? - Stack Overflow

admin管理员组

文章数量:1387396

I have following code in JavaScript

function checkEntries()
{
    if(document.getElementById("username")=="" &&  document.getElementById("password").value=="")
    {
        alert("Please enter username and password");
    }
    if(document.getElementById("username").value=="")
    {
        alert("Please enter username");
    }
    if( document.getElementById("password").value=="")
    {
        alert("Please enter password");
    }
}

and HTML code as

<form name="LoginUser" method="post" action="LoginUser" onsubmit="checkEntries()">
              <table width="78%" height="90" border="0" cellpadding="0" cellspacing="0">
              <tr>
                <td width="47%" align="right" class="textstyle">Username:
                  <label for="username2"></label></td>
                <td width="53%" class="textstyle">
                  <input type="text" name="username" id="username" /><div id="testuser"></div>
                </td>
              </tr>
              <tr>
                <td align="right" class="textstyle">&nbsp;</td>
                <td>&nbsp;</td>
              </tr>
              <tr id="passRow">
                <td align="right" class="textstyle">Password:</td>
                <td><label for="password"></label>
                  <input type="password" name="password" id="password"/>
Forgot Password?? Click here...               
<div id="testpwd"></div></td>
              </tr>
              <tr>
                <td align="right" class="textstyle">&nbsp;</td>
                <td>&nbsp;</td>
              </tr>
              <tr>
                <td align="right" class="textstyle">&nbsp;</td>
                <td><input type="checkbox" name="rempass" id="rempass" />
                  <span class="textstyle">Remember my password</span></td>
              </tr>
              <tr>
                <td align="right" class="textstyle">&nbsp;</td>
                <td class="textstyle">&nbsp;</td>
              </tr>
              <tr>
                <td align="right" class="textstyle">&nbsp;</td>
                <td class="textstyle">
                  <input type="submit" name="login" id="login" value="Sign in" />
                  </td>
              </tr>
            </table>
        </form>

The JavaScript code checks whether the username and password are entered on login form or not. It is working fine. But after showing error, it submits the form.

I want that this form should not be submitted if username and password are not entered. It should just stay on login page. How can I achieve this?

I have following code in JavaScript

function checkEntries()
{
    if(document.getElementById("username")=="" &&  document.getElementById("password").value=="")
    {
        alert("Please enter username and password");
    }
    if(document.getElementById("username").value=="")
    {
        alert("Please enter username");
    }
    if( document.getElementById("password").value=="")
    {
        alert("Please enter password");
    }
}

and HTML code as

<form name="LoginUser" method="post" action="LoginUser" onsubmit="checkEntries()">
              <table width="78%" height="90" border="0" cellpadding="0" cellspacing="0">
              <tr>
                <td width="47%" align="right" class="textstyle">Username:
                  <label for="username2"></label></td>
                <td width="53%" class="textstyle">
                  <input type="text" name="username" id="username" /><div id="testuser"></div>
                </td>
              </tr>
              <tr>
                <td align="right" class="textstyle">&nbsp;</td>
                <td>&nbsp;</td>
              </tr>
              <tr id="passRow">
                <td align="right" class="textstyle">Password:</td>
                <td><label for="password"></label>
                  <input type="password" name="password" id="password"/>
Forgot Password?? Click here...               
<div id="testpwd"></div></td>
              </tr>
              <tr>
                <td align="right" class="textstyle">&nbsp;</td>
                <td>&nbsp;</td>
              </tr>
              <tr>
                <td align="right" class="textstyle">&nbsp;</td>
                <td><input type="checkbox" name="rempass" id="rempass" />
                  <span class="textstyle">Remember my password</span></td>
              </tr>
              <tr>
                <td align="right" class="textstyle">&nbsp;</td>
                <td class="textstyle">&nbsp;</td>
              </tr>
              <tr>
                <td align="right" class="textstyle">&nbsp;</td>
                <td class="textstyle">
                  <input type="submit" name="login" id="login" value="Sign in" />
                  </td>
              </tr>
            </table>
        </form>

The JavaScript code checks whether the username and password are entered on login form or not. It is working fine. But after showing error, it submits the form.

I want that this form should not be submitted if username and password are not entered. It should just stay on login page. How can I achieve this?

• javascript
• html
• forms

Share Improve this question Follow edited Mar 15, 2012 at 11:41 BalusC 1.1m376376 gold badges3.7k3.7k silver badges3.6k3.6k bronze badges asked Mar 15, 2012 at 11:09 Aishwarya ShivaAishwarya Shiva 3,4161616 gold badges6161 silver badges112112 bronze badges

Add a ment  | 

1 Answer 1

Sorted by: Reset to default 4

Try:

function checkEntries() {
   var errFlag = false;
   var errMsg = "";
    var username = document.getElementById("username");
    var password = document.getElementById("password")
   if(username == "") {
      errMsg += "Please enter username.\n";
      errFlag = true;
   }
   if(password == "") {
     errMsg += "Please enter password";
     errFlag = true;
   }
   if(!errFlag) {
      return true;
   }else {
      alert(errMsg);
      return false;
   }
}

And on your onsubmit:

<form name="LoginUser" method="post" action="LoginUser" onsubmit="return checkEntries();">

Hope it helps

本文标签： javascriptHow to block form submitStack Overflow