how to call server control defined in web page through separate javascript file

You need to pass the ID of the control as a parameter of your javascript function.

For reference, see the code below.

Your Javascript file abc.js contains following

function abc(txtID) {
    alert(document.getElementById(txtID).value);
}

HTML page contains,

<script src="abc.js" type="text/javascript"></script>
<asp:textbox id="txtInput" runat="server" ></asp:textbox>
<asp:button id="btn2" runat="server" text="Click Me" />

Then on your server side page load event

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        btn2.Attributes.Add("onclick", "abc('" + txtInput.ClientID + "')");
    }
}

That's it, You are done.



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