Javascript Lawnchair:检查存储及其文档是否存在

我创建了一个Lawnchair商店并保存了它。请参阅以下代码：

var DB = new Lawnchair({ name: "DB", adapter: ["indexed-db", "webkit-sqlite", "ie-userdata", "blackberry-persistent-store", "dom", "window-name", "gears-sqlite", "memory"] });
DB.save({ key: "resKey", res: res});

这里res是一个javascript对象，它是存储的数据

但是当我下次关闭并重新打开网页时，我想检查这个商店是否存在。如果存储存在，我想检查此文档是否存在。如何进行这些检查

谢谢

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PS-有什么好的资源可以让我学习Lawnchair吗

经过多次试验，我终于得出以下结论：

// create a store //* CORRECT TO USE
DB = new Lawnchair({ name: "DB", adapter: ["indexed-db", "webkit-sqlite", "ie-userdata", "blackberry-persistent-store", "dom", "window-name", "gears-sqlite", "memory"] });
//Save a document/table
DB.save({ key: "resKey", data: res }, function () {
    //Access the created store
    DB = Lawnchair({ name: "DB", adapter: ["indexed-db", "webkit-sqlite", "ie-userdata", "gears-sqlite", "blackberry-persistent-store", "dom", "window-name", "memory"] });
    console.log(DB)
    //check if the document exists based on the key we used to create it
    DB.exists("resKey", function (e) {
        console.log("exists : " + e)
        if (e == true) {
        //get all records from the store
            DB.all(function (r) {
                console.log(r);
        //remove all document/table from the store
                DB.nuke(function () {
                    console.log("Data nuke-ed");
            //check if the document exists based on the key we used to create it
                    DB.exists("resKey", function (e) {
                        console.log("exists : " + e)
                        if (e == true) {
                //get all records from the store
                            DB.all(function (r) {
                                console.log(r);
                            });
                        } else {
                            console.log("Data deleted");
                        }
                    });
                });
            });
        } else {

        }
    });
});

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请让我知道这是正确的方法还是有更好的方法。如果您喜欢我的努力，请给我分：）

但是我不知道如何检查商店是否存在，但是我能够检查表/文档是否存在。有人能带我到这里吗？