Please find the error in below written code for asp + JavaScript

<script type=text/javascript>
function abc()
{
   return confirm('Are u sure');
}
</script>


<asp: Button id="btnSubmit" runat="server" onClick="btnSubmit_Click" onClientClick="abc" Text="Submit/>

When I click the button the message box appears 开发者_JAVA百科if I hit the cancel Button still the function for onClick is called instead it should not. But if I write JavaScript code directly in the tag it works properly.

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onClientClick="return abc()"

the return is the essential bit.