Stopping onclick from firing when onclientclick is false?

Question

Is it possible to use the onclientclick property of a button to do a clientside check. If the check returns true, then fire the onclick event. If the clientside check returns false, don't fire the onclick event.

Is that possible?

UPDATE:

These 2 work:

Stops the form from submitting:
OnClientClick="return false;"

---

Allows the form to submit:
OnClientClick="return true;"

---

The next 2 do not work:

// in js script tag
function mycheck() {
    return false;
}

// in asp:button tag
OnClientClick="return mycheck();"

---

// in js script tag
function mycheck() {
    return true;
}

// in asp:button tag
OnClientClick="return mycheck();"

It submits the form both times.

Why is that?

Answer 1

You want to add return inside OnClientClick after a function is called. Otherwise, the button will post back even if function returns false.

<asp:button ID="Button1" runat="server" OnClick="Button1_Click" 
    OnClientClick="return checkValidation()" Text="Submit" />

<script type="text/javascript">
    function checkValidation() {
        return confirm('Everything ok?');
    }
</script>