//js中的数组可以以键值对的方式存在         var arr = new Array();         arr["A"] = "boss";         arr["B"] = "Emp";         for (var m in arr) {             document.write(arr[m] + " ");         }         var person = new Object();         person["name"] = "xiaoli";         person["age"] = "18";         person["salary"] = "1888.9";         for (var p in person) {             document.write(person[p] + "<br>");         }         //测试使用有age属性呢？         if (typeof person["age"] == "undefined") {             document.write("no");         }