--- title: IDBObjectStore.autoIncrement slug: Web/API/IDBObjectStore/autoIncrement translation_of: Web/API/IDBObjectStore/autoIncrement ---

{{ APIRef("IndexedDB") }}

{{domxref("IDBObjectStore")}}的只读属性autoIncrement接口返回当前objectStore的自增标记值（true或false）。

什么是自增呢？熟悉SQL的朋友应该知道，SQL数据里面的字段可以设置自增，当一条记录被插入时，不必传入该字段，新记录的该字段值会在前面一条记录该字段值的基础上加1.而indexedDB里面的autoIncrement的同样的意义。（译者注）

注意：每个objectStore的auto increment计数器是分开独立的。

{{AvailableInWorkers}}

句法

var myAutoIncrement = objectStore.autoIncrement;

Value

{{domxref("Boolean")}}:

值 含义
true 当前objectStore会自增
false 当前objectStore不会自增
 

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.autoIncrement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.autoIncrement);

  // 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-autoIncrement', 'autoIncrement')}} {{Spec2('IndexedDB')}}  
{{SpecName("IndexedDB 2", "#dom-idbobjectstore-autoincrement", "autoIncrement")}} {{Spec2("IndexedDB 2")}}  

浏览器兼容性

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

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