无法获取属性个未定义或空引用 UWP

Question

我的 visual studio 中有以下代码，它在我的桌面 win10 上的 UWP 应用程序中运行良好，尽管它不适用于我的 windows phone 作为UWP 应用程序。我还尝试了运行我的简单 web 应用程序，来自网络服务器并将其加载到 Edge 中，它运行良好。应该是什么问题？我的代码看起来像这样。我省略了一些部分：

var model = {
    db: {},
    goalsobj: {},
    goals: [],
    init: function() {
        var openReq = window.indexedDB.open("GoalsDB");
        openReq.onupgradeneeded = function (event) {
            model.db = event.target.result;
            var objectStore = model.db.createObjectStore("Goals", { keyPath: "id" });
            objectStore.createIndex("id","id", {unique:true});
        };
        openReq.onsuccess = function (event) {
            model.db = event.target.result
            model.db.transaction("Goals", "readonly").objectStore("Goals").count().onsuccess = function (event) {
                if (event.target.result == 0) {
                    console.log("indexeddb empty");
                    var goalstemplate = {
                        id: "idee",
                        goals: [{ "name": "Task1" }, { "name": "Task2" }, { "name": "Task3" }]
                        }
                    var addReq = model.db.transaction("Goals", "readwrite").objectStore("Goals").add(goalstemplate);
                } else {
                    model.db.transaction("Goals", "readonly").objectStore("Goals").get("idee").onsuccess = function (e) {
                        model.goalsobj = e.target.result;
                        //console.log(e.target.result);
                        model.goals = model.goalsobj.goals;
                        goalfunc.makeList(); //model should not talk to view, but this case it is amust, because if I remove this, it does not render at boot.
                        }

                }

            }
    openReq.onerror = function (event) {
        console.log("Operation failed");
    }

}
    },
    add: function(goalname) {
        model.goals.push(
            {
                "name": goalname
        });
        model.savedb();
    },
    move: function (id,updown) {
        if (updown == "up") {
            model.goals.splice((id-1), 0, model.goals.splice(id, 1)[0]);
        };
        if (updown == "down") {
            model.goals.splice((id+1), 0, model.goals.splice(id, 1)[0]);
        };
    },
    savedb: function(){ 
        //console.log(goals);
        var update = model.db.transaction("Goals", "readwrite").objectStore("Goals").put(model.goalsobj);
        update.onerror = function (event) {
            console.log(event);
        };

},
};

现在，当我在我的设备上运行这个条件时，它说： ms-appx-web://1318f74a-397e-4958-aa6b-c8d11b7c5dce/js/main.js

中第 28 行第 25 列的未处理异常

0x800a138f - JavaScript 运行时错误：无法获取属性 'goals' 未定义或空引用

Answer 1

我已经在我的设备（设备：Microsoft RM-1118 OSVersion:WindowsMobile 14393）中测试了您的代码。它工作正常。如您所见，我在 html 页面上放置了一个按钮。点击按钮的动作会执行model.init()，然后我在model.goals = model.goalsobj.goals;设置断点。当第二次点击按钮时，model.goals 将被设置为正确的值。

所以我认为问题可能发生在您的目标设备上，或者您的 GoalsDB 已损坏。因为 Unable to get property 'goals' of undefined or null reference 的原因是 model.goalsobj 没有设置正确的值。请检查那些操作是否改变了你的数据库结构，比如移动操作。您可以显示有关目标设备的更多详细信息，我会帮助您。

(function () {
    document.getElementById("createDatabase").addEventListener("click", createDB, false);
    function createDB() {   
        model.init();
    }
})();
var model = {
    db: {},
    goalsobj: {},
    goals: [],
    init: function () {
        var openReq = window.indexedDB.open("GoalsDB");
        openReq.onupgradeneeded = function (event) {
            model.db = event.target.result;
            var objectStore = model.db.createObjectStore("Goals", { keyPath: "id" });
            objectStore.createIndex("id", "id", { unique: true });
        };
        openReq.onsuccess = function (event) {
            model.db = event.target.result
            model.db.transaction("Goals", "readonly").objectStore("Goals").count().onsuccess = function (event) {
                if (event.target.result == 0) {
                    console.log("indexeddb empty");
                    var goalstemplate = {
                        id: "idee",
                        goals: [{ "name": "Task1" }, { "name": "Task2" }, { "name": "Task3" }]
                    }

                    model.db.transaction("Goals", "readwrite").objectStore("Goals").add(goalstemplate);

                } else {
                    model.db.transaction("Goals", "readonly").objectStore("Goals").get("idee").onsuccess = function (e) {

                        model.goalsobj = e.target.result;
                        //console.log(e.target.result);
                        if (model.goalsobj.goals != undefined) {
                            model.goals = model.goalsobj.goals;
                        } else {
                            console.log(e.target.result);
                        }

                       //goalfunc.makeList(); //model should not talk to view, but this case it is amust, because if I remove this, it does not render at 
                    }
                }
            }
            openReq.onerror = function (event) {
                console.log("Operation failed");
            }
        }
    },
    add: function (goalname) {
        model.goals.push(
            {
                "name": goalname
            });
        model.savedb();
    },
    move: function (id, updown) {
        if (updown == "up") {
            model.goals.splice((id - 1), 0, model.goals.splice(id, 1)[0]);
        };
        if (updown == "down") {
            model.goals.splice((id + 1), 0, model.goals.splice(id, 1)[0]);
        };
    },
    savedb: function () {
        //console.log(goals);
        var update = model.db.transaction("Goals", "readwrite").objectStore("Goals").put(model.goalsobj);
        update.onerror = function (event) {
            console.log(event);
        };
    }
};

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