I am trying to implement try/catch scope in my JSOM, but I am getting the error message in the question's title.

Below is my code:

        errScope = new SP.ExceptionHandlingScope(context);
        var scopeStart = errScope.startScope();

        var tryBlock = errScope.startTry();
            var targetList = context.get_web().get_lists().getByTitle("Announcements");
            //constructing caml
            var query = new SP.CamlQuery();
            var caml = "<View><Query><Where><Neq><FieldRef Name='Title'/>";
            caml += "<Value Type='Text'>Excluded</Value></Neq></Where></Query>";
            caml += "<RowLimit>2</RowLimit>";
            caml += "</View>";
            query.set_viewXml(caml);
            var listItems = targetList.getItems(query);
            results = context.loadQuery(listItems, 'Include(Title, Author, ID)')
            targetList = context.get_web().get_lists().getByTitle("Announcements");
        tryBlock.dispose();
        context.executeQueryAsync(_onSucceed, _Fail)

        var catchBlock = errScope.startCatch();
        catchBlock.dispose();



        var finallyBlock = errScope.startFinally();
        finallyBlock.dispose();

When it reaches the end of the try block, it throws the error:

Uncaught Error: Incorrect usage of exception handling scope.

Also I don't know what are the best practices to put in the catch block and finally block.