on button onclick event not fire after onclientclick

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ASP.NET

After OnClientClick event OnClick event not fire.
My code as follows.

function permissions() {
            var add = 1;
            if (add == 0) {
                alert("You have no permissions to Add Record");
                return false;
            }
            else
                return true;
        }

<asp:Button ID="btn_new" CssClass="btn btn-sm btn-success" runat="server" Text="Add New" onclick="btn_new_Click" OnClientClick="javascript:return permissions();" />

what issue in my code? if not So why it not work well, please Provide Working Solutions..!!