$.inArray(dmy, availableDates) 返回元素的索引，所以当你与 1 比较时，只有 14-5-2011 会匹配.检查不等于-1.应该可以.

$.inArray(dmy, availableDates) returns the index of the element, so when you compare with 1 only 14-5-2011 will match. Check for not equal to -1. Should work.

小提琴 - http://jsfiddle.net/yXMKC/4/

var availableDates = ["9-5-2011","14-5-2011","15-5-2011"];

function available(date) {
  dmy = date.getDate() + "-" + (date.getMonth()+1) + "-" + date.getFullYear();
  console.log(dmy+' : '+($.inArray(dmy, availableDates)));
  if ($.inArray(dmy, availableDates) != -1) {
    return [true, "","Available"];
  } else {
    return [false,"","unAvailable"];
  }
}