How to call javascript code from server side

One can call JavaScript client side function directly from code behind using RegisterStartupScript. If one wants JavaScript to be embedded into codebehind, then make use of RegisterClientScriptBlock:

<script>
function fnShowMessage()
{
       alert(" Invoke Javascript function from Server Side Code Behind ");
 }
 </script>

protected void Button1_Click(object sender, EventArgs e)
{
        ClientScript.RegisterStartupScript (GetType(),"Javascript", "javascript: fnShowMessage(); ",true);
}
protected void Button2_Click(object sender, EventArgs e)
{
       ClientScript.RegisterClientScriptBlock(GetType(), "Javascript",  "<script>alert('Record Added Successfully')</script>");
}