From 33058f2b292b3a581333bdfb21b8f671898c5060 Mon Sep 17 00:00:00 2001 From: Peter Bengtsson Date: Tue, 8 Dec 2020 14:40:17 -0500 Subject: initial commit --- .../web/api/idbobjectstore/keypath/index.html | 115 +++++++++++++++++++++ 1 file changed, 115 insertions(+) create mode 100644 files/zh-cn/web/api/idbobjectstore/keypath/index.html (limited to 'files/zh-cn/web/api/idbobjectstore/keypath') diff --git a/files/zh-cn/web/api/idbobjectstore/keypath/index.html b/files/zh-cn/web/api/idbobjectstore/keypath/index.html new file mode 100644 index 0000000000..e99f1ae519 --- /dev/null +++ b/files/zh-cn/web/api/idbobjectstore/keypath/index.html @@ -0,0 +1,115 @@ +--- +title: IDBObjectStore.keyPath +slug: Web/API/IDBObjectStore/keyPath +translation_of: Web/API/IDBObjectStore/keyPath +--- +

{{ APIRef("IndexedDB") }}

+ +
+

{{domxref("IDBObjectStore")}}的只读属性keyPath接口返回当前objectStore的key path。

+ +

什么是keyPath呢？在indexedDB中，一条记录就是一个object，object里面有一个属性作为这条记录的主要依据用来进行查询，而这个属性的属性名就是keyPath，属性值就是key。在用indexedDB的get方法时，提供key，而不需要指定keyPath，因为get方法把参数作为这个最主要的属性的值，在数据库中进行查询。（译者注）

+ +

如果该属性值为null，应用中必须在每一次进行修改性质的操作时提供一个key。

+ +

add、put方法都可以传第二个参数，当你当前的objectStore的autoIncrement为true时，你一般不会设置keyPath，如果这个时候你在put的时候不提供第二个参数，indexedDB就不知道要更新哪一条记录了。（译者注）

+
+ +

{{AvailableInWorkers}}

+ +

句法

+ +
var mykeyPath = objectStore.keyPath;
+ +

Value

+ +

任何类型。

+ +

例子

+ +

在下面代码片段中，我们在数据库里打开了一个可读写的事务（transaction），并且用add()向一个objectStore中添加了一些数据。在objectStore被创建之后，我们在console中打印了objectStore.keyPath的值。想查看完整的例子，请查看我们的To-do Notifications应用（查看在线例子）。

+ +
// Let us open our database
+var DBOpenRequest = window.indexedDB.open("toDoList", 4);
+
+DBOpenRequest.onsuccess = function(event) {
+  note.innerHTML += '<li>Database initialised.</li>';
+
+  // store the result of opening the database in the db variable.
+  // This is used a lot below
+  db = DBOpenRequest.result;
+
+  // Run the addData() function to add the data to the database
+  addData();
+};
+
+function addData() {
+  // Create a new object ready to insert into the IDB
+  var newItem = [ { taskTitle: "Walk dog", hours: 19, minutes: 30, day: 24, month: "December", year: 2013, notified: "no" } ];
+
+  // open a read/write db transaction, ready for adding the data
+  var transaction = db.transaction(["toDoList"], "readwrite");
+
+  // report on the success of the transaction completing, when everything is done
+  transaction.oncomplete = function(event) {
+    note.innerHTML += '<li>Transaction completed.</li>';
+  };
+
+  transaction.onerror = function(event) {
+  note.innerHTML += '<li>Transaction not opened due to error. Duplicate items not allowed.</li>';
+  };
+
+  // create an object store on the transaction
+  var objectStore = transaction.objectStore("toDoList");
+  console.log(objectStore.keyPath);
+
+  // Make a request to add our newItem object to the object store
+  var objectStoreRequest = objectStore.add(newItem[0]);
+
+  objectStoreRequest.onsuccess = function(event) {
+    // report the success of our request
+    note.innerHTML += '<li>Request successful.</li>';
+  };
+};
+ +

规范

+ + + + + + + + + + + + + + + + + + + +
规范状态备注
{{SpecName('IndexedDB', '#widl-IDBObjectStore-keyPath', 'keyPath')}}{{Spec2('IndexedDB')}} 
{{SpecName("IndexedDB 2", "#dom-idbobjectstore-keypath", "keyPath")}}{{Spec2("IndexedDB 2")}} 
+ +

浏览器兼容性

+ +
+ + +

{{Compat("api.IDBObjectStore.keyPath")}}

+
+ +

相关内容

+ + -- cgit v1.2.3-54-g00ecf