For disable custom errors you need navigate to C:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\TEMPLATE\LAYOUTS and Open the web.config and make the CustomErrors off <customErrors mode="Off" />
var ctx = new SP.ClientContext.get_current(); var web = ctx.get_web(); //Geting reference to the list var olist = web.get_lists().getByTitle( 'Configs' ); var oitem = olist.getItemById(1); //get Title,id,ConfigItem fields ctx.load(oitem, "Title" , "Id" , "ConfigItem" ); ctx.executeQueryAsync( function () { alert(oitem.get_item( "Title" )); alert(oitem.get_item( "ConfigItem" )); }, function (a, b) { alert(b.get_message()); });