I need to change the below code:
$("#ctl00_PlaceHolderMain_SPWebPartManager_g_3c1ba10a_23ec_4ab5_b303_18f8bd7ee7e7_ctl00_btnAdd").attr("disabled", true);
To this:
var ControlID = "#ctl00_PlaceHolderMain_SPWebPartManager_g_3c1ba10a_23ec_4ab5_b303_18f8bd7ee7e7_ctl00_btnAdd"
$(ControlID).attr("disabled", true);
But the above one not working .. what is the error ?