html5 geoLocation

1. 判斷用戶的瀏覽器是否支持html5定位, navigator.geolocation是否存在

2. navigator.geolocation有三個方法
　　=> void navigator.geolocation.getCurrentPosition(onSuccess, onError, options) 獲取用戶當前位置
       => int watchCurrentPosition(onSuccess,onError,options) 持續獲取當前用戶位置
       => void clearWatch(watchId) watchId 爲watchCurrentPosition返回的值  取消監控

3. 例子+描述

if (navigator.geolocation) {  
    navigator.geolocation.getCurrentPosition(locationSuccess, locationError,{  
        // 指示瀏覽器獲取高精度的位置，默認爲false  
        enableHighAcuracy: true,  
        // 指定獲取地理位置的超時時間，默認不限時，單位爲毫秒  
        timeout: 5000,  
        // 最長有效期，在重複獲取地理位置時，此參數指定多久再次獲取位置。  
        maximumAge: 3000  
    });  
}else{  
    alert("Your browser does not support Geolocation!");  
}  
locationError: function(error){  
    switch(error.code) {  
        case error.TIMEOUT:  
            showError("A timeout occured! Please try again!");  
            break;  
        case error.POSITION_UNAVAILABLE:  
            showError('We can\'t detect your location. Sorry!');  
            break;  
        case error.PERMISSION_DENIED:  
            showError('Please allow geolocation access for this to work.');  
            break;  
        case error.UNKNOWN_ERROR:  
            showError('An unknown error occured!');  
            break;  
    }  
}  
locationSuccess: function(position){  
    var coords = position.coords;
    var timestamp = position.timestamp;
    console.log("latitude="+coords.latitude+" longitude is " + coords.longitude + " use time is " + timestamp)
    );
}