我正在使用phonegap1.8.0，我想检测网是否可用，然后我是否可以访问它。在phonegap doc公开以下api
navigator.network.isReachable('www.facebook.com', reachCallBack, {});
然而，我得到了
Console(4820): Uncaught TypeError: Object #<Object> has no method 'isReachable' at file:///android_asset/www/index.html:71
代码是：
function netIsAvailable()
{
var reachCallBack = function (reachability)
{
var networkState = reachability.code || reachability;
var states = {};
states[NetworkStatus.NOT_REACHABLE] = 'No network connection';
states[NetworkStatus.REACHABLE_VIA_CARRIER_DATA_NETWORK] = 'Carrier data connection';
states[NetworkStatus.REACHABLE_VIA_WIFI_NETWORK] = 'WiFi connection';
alert('Connection type: ' + states[networkState]);
};
alert( navigator.onLine );
navigator.network.isReachable('www.facebook.com', reachCallBack, {});
}