javascript - 为什么将 JSONObject 放入 indexedDB 数据库时会出错？

Question

我目前正在尝试运行 indexedDB 数据库。但是，我正在努力解决有关 indexedDB 的 put 方法的一些问题。虽然定义了keypath，并且移交的JSONObject包含一个与定义的keypath命名方式相同的值，但put方法会导致以下错误：

未捕获的 DOMException：无法在“IDBObjectStore”上执行“放置”：评估对象存储的键路径未产生值。

为了确保 JSONObject 确实包含应用作键的值，我正在记录该对象。这就是它的样子：

{"key":102019,"month":10,"year":2019,"spendings":[{"type":{"name":"Technology","importance":70,"iconURL":". /Resources/Technology.png"},"cost":"1500","name":"Macbook pro","timestamp":1571696285911}],"budget":0}

用于存储数据的代码如下：

function callbackSaveSpendingMonth(database, spendingMonth) {

    let userName = defaultUserName;
    let transaction = database.transaction(userName, "readwrite");
    let objectStore = transaction.objectStore(userName, { keyPath: 'key' });
    let JSONspendingMonth = JSON.stringify(spendingMonth);

    console.log(JSONspendingMonth);

    let request = objectStore.put(JSONspendingMonth);
    request.onsuccess = function (event) {
        console.log("The month " + spendingMonth.getMonth() + "/" + spendingMonth.getYear() + " has been saved successfully!");
    }

    transaction.oncomplete = function (event) {
        console.log("A connection to indexedDB has successfully been established!");
    }
}