jQuery tagEditor的autocomplete自动填充的配置项参数selectFirst不起作用?

$('#demo').tagEditor({
                autocomplete: { delay: 0, position: { collision: 'flip' }, source: ['ActionScript', 'AppleScript', 'Asp', 'BASIC', 'C', 'C++', 'CSS', 'Clojure', 'COBOL', 'ColdFusion', 'Erlang', 'Fortran', 'Groovy', 'Haskell', 'HTML', 'Java', 'JavaScript', 'Lisp', 'Perl', 'PHP', 'Python', 'Ruby', 'Scala', 'Scheme'],selectFirst:true },
                forceLowercase: false,
                placeholder: 'Programming languages ...'
            });

加了个 selectFirst:true 没起作用，why?