Javascript 变量拒绝在jQuery.get回调函数中取值

我检测一个值是否存储在localStorage中（如果localStorage存在），如果它不在数据库中（或者用户没有带有localStorage的浏览器），那么我运行一个AJAX GET请求

if (Modernizr.localstorage) {
    // there is storage
    artist = localStorage.getItem('artist');
    if (!artist) {
        // but no cache
        artist = fetchArtist();
        localStorage.setItem('artist', artist)
    }
} else {
    // there's no storage
    artist = fetchArtist();
}
function fetchArtist() {
    var fetchedArtist;
    var recentTracks;
    $.get('script.php', [], function(data) {
        recentTracks = data.recenttracks;
        fetchedArtist = ((recentTracks !== undefined) ? recentTracks.track.artist['#text'] : 'Last.fm connection failed.');
    }, 'json');
    return fetchedArtist;
}

---

php只获取一个JSON字符串，jQuery将其转换为数据对象。我可以看出问题所在：因为$.get是异步的，所以在函数可以分配我所追求的值之前，会返回fetchedArtist变量，但是我想不出一个整洁的方法来实现这一点（可能是全局变量，但我真的不希望）。我可以在$.get中对fetchedArtist变量和我要查找的值进行console.log，但是fetchArtist函数总是返回未定义的值。

您必须通过从

fetchArtister（）中删除返回语句来异步化工作流

函数，因为由于

$.get

请求的异步行为，它无法执行您需要的操作

试着这样做：

if (Modernizr.localstorage) {
    // there is storage
    var artist = localStorage.getItem('artist');
    if (!artist) {
        // but no cache
        fetchArtist();
    } else {
        doWhatYouNeedWithArtist( artist );
    }
} else {
    // there's no storage
    fetchArtist();
}

function fetchArtist() {
    var fetchedArtist;
    var recentTracks;
    $.get('script.php', [], function(data) {
        recentTracks = data.recenttracks;
        fetchedArtist = ((recentTracks !== undefined) ? recentTracks.track.artist['#text'] : 'Last.fm connection failed.');
        if ( Modernizr.localstorage ) {
                Modernizr.localstorage.setItem('artist', fetchedArtist);
        }
        // then do your stuff
        doWhatYouNeedWithArtist( fetchedArtist );
    }, 'json');
}

function doWhatYouNeedWithArtist( artists ) {
    // do stuff
}

希望这有帮助！再见