反射，减少对全局变量的污染

<script type="text/javascript">
    /*反射*/
    typeof flight.number     //'number'
    typeof flight.status    //'string'
    typeof flight.arrival    //'object'
    typeof flight.manifest    //'undefined'

    typeof flight.toString     //'function'
    typeof flight.constructor//'function'

    flight.hasOwnProperty('number')        //true
    flight.hasOwnProperty('constructor')//false

    /*减少全局变量的污染*/
    全局变量削弱了程序的灵活性，尽量避免
    var Mapp={};
    Mapp.stooge={
        "first-name":"Joe",
        "last-name":"Howard"
    };
    Mapp.flight={
        airline:"Oceanic",
        number:815,
        departure:{
            IATA:"SYD",
            time:"2004-09-22 14:55",
            city:"Sydney"
        },
        arrival:{
            IATA:"LAX",
            time:"2004-09-23 10:42",
            city:"Los Angeles"
        }
    };
    </script>