Assuming you want to answer javascript
var result=confirm("Confirmation messsage goes here");
if(result)
alert("user press ok");
else
alert("user press cancel");
for c# winform
if (MessageBox.Show("Confirmation messsage goes here", "Confirmation", MessageBoxButtons.YesNo, MessageBoxIcon.Warning, MessageBoxDefaultButton.Button1) == DialogResult.Yes)
return true;
else
return false;
hope you may got idea, and it will help you.