[PWA] 18. Clean the photo cache

最新推荐文章于 2025-09-10 21:04:03 发布

转载最新推荐文章于 2025-09-10 21:04:03 发布 · 73 阅读

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原文链接：http://www.cnblogs.com/Answer1215/p/5516091.html

本文介绍了一种定期清理不再显示于页面上的图片缓存的方法。通过从数据库中获取所有消息并提取需要保留的图片URL，然后检查缓存中的每张图片是否在保留列表内，不在则删除。该方法确保了缓存的有效利用。

We cannot let photo always keep caching new data without clean the old data. If message is not display on the page anymore, we want to clean it. And also every 5 mins we want to clean the photo data.

export default function IndexController(container) {
    this._container = container;
    this._postsView = new PostsView(this._container);
    this._toastsView = new ToastsView(this._container);
    this._lostConnectionToast = null;
    this._dbPromise = openDatabase();
    this._registerServiceWorker();
    this._cleanImageCache();

    var indexController = this;

    setInterval(function () {
        indexController._cleanImageCache();
    }, 1000 * 60 * 5);

    this._showCachedMessages().then(function () {
        indexController._openSocket();
    });
}

_leanImageCache():

First, go to idb, get all the writtrs from the db and get the photos which we want to keep
Then open the photo cache and check the url exists in the list, if not then delete it.

IndexController.prototype._cleanImageCache = function () {
    return this._dbPromise.then(function (db) {
        if (!db) return;

        // TODO: open the 'wittr' object store, get all the messages,
        // gather all the photo urls.
        //
        // Open the 'wittr-content-imgs' cache, and delete any entry
        // that you no longer need.
        var photosToKeep = [];
        var tx = db.transaction('wittrs');
        return tx.objectStore('wittrs').getAll()
            .then(function(messages){
                messages.forEach(function(message){
                    if(message.photo){
                        photosToKeep.push(message.photo);
                    }
                });

                return caches.open('wittr-content-imgs');
            })
            .then(function(cache){
                return cache.keys().then(function(requests){
                    requests.forEach(function(request){
                        var url = new URL(request.url);
                        if(!photosToKeep.includes(url.pathname)){
                            cache.delete(request);
                        }
                    })
                })
            });
    });
};

转载于:https://www.cnblogs.com/Answer1215/p/5516091.html