给定索引，如何读取 indexeddb 自动增量对象存储中的对象键

Question

代码形式的这个问题，我可以使用.put(doc, key)覆盖对象，但我不知道如何读取它的密钥

// After writing doc1 to an autoincrement
// objectStore, I want to overwrite it 
// later, I only know its index 
// (not its key)

var docs = [
  {'a':'doc1', 'my_index': 'anindex'},
  {'a':'doc2', 'my_index': 'anindex'}
];

indexedDB.deleteDatabase('foo').onsuccess = function () { 

  var idb;
  var req = indexedDB.open('foo');

  function writeDocs(docs) {

    if (!docs.length) { 
      console.log('done writing');
      return;
    }

    var txn = idb.transaction(['some_store_name'], 'readwrite');
    var doc = docs.shift();
    console.log('writing', doc);

    var get = txn.objectStore('some_store_name').index('my_index')
      .get(doc.my_index);

    get.onsuccess = function(e) { 

      var key = null;

      if (e.target.result) { 
        // If there is a result here, I want to overwrite it
        // to do that I need its key, cant find it here?    
        console.log(e.target.result);
      }

      var dataReq = txn.objectStore('some_store_name').put(doc);

      dataReq.onsuccess = function (e) {
        console.log('wroted', e.target.result);
        writeDocs(docs);
      }

      dataReq.onerror = function () { 
        console.log('it broke');
        writeDocs(txn, docs);
      }
    }
  };

  req.onupgradeneeded = function(e) {
    var db = e.target.result;
    db.createObjectStore('some_store_name', {autoIncrement : true})
      .createIndex('my_index', 'my_index', {unique: true});
  };

  req.onsuccess = function(e) { 
    idb = e.target.result;
    writeDocs(docs);
  };
}

Answer 1

  if (e.target.result) {
    // If there is a result here, I want to overwrite it
    // to do that I need its key, cant find it here?    
    console.log(e.target.result);
  }

e.target.result其实是关键！但仅作为对put 或add 的回应，而不是get。您可以使用此值来put() 将来的数据。

没有行键，就像你有：objectstore.put(data, key)

使用内联键，您只需 objectstore.put(data)

更新：问题是您正在循环 writeDocs，但在您的第一个循环中，key 是 null，因此会引发错误。

Here's a working example.

第二次更新：看起来可能已经添加了一些代码，或者我之前错过了一些东西。除了我在上面标记的内容之外，您的索引是unique，并且您两次使用相同的my_index 值，因此第二个put() 出现错误。我在我的小提琴解决方案中通过使 my_index 每个页面加载唯一来避免这个问题。

Answer 2

已编辑：对此的简单解决方案是使用index.getKey(indexVal)，切换到内联键也可以，但会导致迁移混乱。将db.createObjectStore('some_store_name', {autoIncrement : true}).createIndex('my_index', 'my_index', {unique: true}); 更改为db.createObjectStore('some_store_name', {keyPath: 'seq', autoIncrement : true}).createIndex('my_index', 'my_index', {unique: true});

// After writing doc1 to an autoincrement
// objectStore, I want to overwrite it 
// later, I only know its index 
// (not its key)

var docs = [
  {'a':'doc1', 'my_index': 'anindex'},
  {'a':'doc2', 'my_index': 'anindex'}
];

indexedDB.deleteDatabase('foo').onsuccess = function () { 

  var idb;
  var req = indexedDB.open('foo');

  function writeDocs(docs) {

    if (!docs.length) { 
      console.log('done writing');
      return;
    }

    var txn = idb.transaction(['some_store_name'], 'readwrite');
    var doc = docs.shift();

    var get = txn.objectStore('some_store_name').index('my_index')
      .get(doc.my_index);

    get.onsuccess = function(e) {

      if (e.target.result) { 
        doc.seq = e.target.result.seq;
      }
      var dataReq = txn.objectStore('some_store_name').put(doc);

      dataReq.onsuccess = function (e) {
        console.log('wroted', e.target.result);
        writeDocs(docs);
      }

      dataReq.onerror = function () { 
        console.log('it broke');
        writeDocs(txn, docs);
      }
    }
  };

  req.onupgradeneeded = function(e) {
    var db = e.target.result;
    db.createObjectStore('some_store_name', {keyPath: 'seq', autoIncrement : true})
      .createIndex('my_index', 'my_index', {unique: true});
  };

  req.onsuccess = function(e) { 
    idb = e.target.result;
    writeDocs(docs);
  };
}