为什么某些代码行在循环后不能执行?
问题描述:
我是javascript的新手,并试图玩API,我不知道为什么在for循环完成后,有些代码行不执行。任何人都可以帮我吗?为什么某些代码行在循环后不能执行?
function jsonFlickrApi(data) {
if (data.stat != 'ok') {
alert('no image loaded');
} else {
for (var i = 0; i <= data.photos.photo.length; i++) {
addImage(data.photos.photo[i].url_o);
var lat = data.photos.photo[i].latitude;
var lon = data.photos.photo[i].longitude;
var LatLon = {
lat: parseFloat(lat),
lng: parseFloat(lon)
};
var markers = new google.maps.Marker({
'position': LatLon,
'map': map,
});
console.log("i", i);
photoMarkers.push(markers);
//It still executes well here.
};
//After the loop is finished, it doesn't print out anything to the console.
console.log("here");
};
//The following line doesn't execute too
fitMap(photoMarkers);
}
答
该循环没有完成,它会引发异常。打开Web控制台看到的细节,你会发现这样的:
Uncaught TypeError: Cannot read property 'url_o' of undefined
数组索引是通过0
length-1
,所以你希望你的for
循环是< data.photos.photo.length
,不<= data.photos.photo.length
。在<=
循环的最后一次迭代中,data.photos.photo[i]
为undefined
,所以试图获得data.photos.photo[i].url_o
的值抛出。
非常感谢,它帮助我很多:) –