I have this java script validation function that fires when the client clicks btnsave if the text of the text box is empty then a message box is displayed and the focus is on the text box but i cannot seem to prevent the page from posting back when the validation fails AM I missing something. here is my code

function validate() 
  {
      var itemscanned;
      itemscanned = document.getElementById('txtItemCode');
      if (itemscanned.value == '') 
      {
          alert("Plz Enter Item Code");
          return false;
         itemscanned.focus
      }
      else 
      {
          alert(itemscanned.value);
      }
  }

I have this java script validation function that fires when the client clicks btnsave if the text of the text box is empty then a message box is displayed and the focus is on the text box but i cannot seem to prevent the page from posting back when the validation fails AM I missing something. here is my code

function validate() 
  {
      var itemscanned;
      itemscanned = document.getElementById('txtItemCode');
      if (itemscanned.value == '') 
      {
          alert("Plz Enter Item Code");
          return false;
         itemscanned.focus
      }
      else 
      {
          alert(itemscanned.value);
      }
  }

• javascript
• asp
• validation

• Is this the submit button for the form? – Mike Perrenoud Commented Dec 28, 2012 at 13:25

4 Answers 4

Write return before function name like this

   <asp:Button ID="btnSave" runat="server" Text="Save" CssClass="buttons"  OnClientClick="return validate()"/>

If this is an ASP.NET WebForms application, you really should consider using the Validator controls. They handle all of client-side logic you are asking for.

If you are using MVC, there is also a way to do model validation on the client side.

add this if its asp button control

OnClientClick = "return validate();"

if it is html button add this

onclick = "return validate();"

Ît belongs how you handle the events. Please show the asp markup and the binding of the javascript event.

You can try to stop event propagation using javascript:

event.stopPropagation();

Read about it here: https://developer.mozilla/en-US/docs/DOM/event.stopPropagation

Note: you have to get the event as an parameter to the validate function:

function validate(event) {

    var itemscanned;    
    itemscanned = document.getElementById('txtItemCode');
    if (itemscanned.value == '') {
        alert("Plz Enter Item Code");
        event.stopPropagation();
        itemscanned.focus
        return false;
    }
    else
    {
        alert(itemscanned.value);
    }
}​

Hope this helps. It's very important how you bind the validate function the button, because asp generates a lot of javascript on its own (google for asp client validation).