How to call javascript function on document.ReadyState inside updatepanel?

I can not call javascript function asynchronosly inside UpdatePanel1 when document.getElementById(‘<%= GridView1.ClientID %>’).readyState !== “complete”. When Button1 fires it works asynchoronosly on server side but does not work on client side and so it does not call javascript function.

Here is my UpdatePanel1:

 <asp:UpdatePanel ID="UpdatePanel1" UpdateMode ="Conditional" ChildrenAsTriggers= "true" runat="server" >
     <Triggers>
         <asp:AsyncPostBackTrigger ControlID="ButtonLoadGridView" /> 
         <asp:AsyncPostBackTrigger ControlID="Button_test2" />   
         <asp:AsyncPostBackTrigger ControlID="Button_test3" />               
     </Triggers>                
  <ContentTemplate>`

My Button: ID=”ButtonLoadGridView”:

protected void ButtonLoadGridView_Click(object sender, EventArgs e)
{
    GridView1.DataSource = "dsData";
    GridView1.DataBind();
}

Here is javascript code need to call when GridView1 is ready:

document.onreadystatechange = function () 

    {
            if (document.getElementById('<%= GridView1.ClientID %>').readyState !== "complete") 
        
        {
     
            window.onload = function ti() 

        {     

        
                document.getElementById('<%= Label_Clients.ClientID %>').scrollIntoView({ behavior: 'smooth' });
                alert("Your data is loaded');

        }
     }
  }
            

What I expect is that this simple javascript code from above:

 document.getElementById('<%= Label_Clients.ClientID %>').scrollIntoView({ behavior: 'smooth' });
                alert("Your data is loaded');

be called after when GridView1 is ready but it does not work asynchoronosly in UpdatePanel