IDBIndex.unique

 The unique read-only property returns a boolean that states whether the index allows duplicate keys.   This is decided when the index is created, using the IDBObjectStore.createIndex method. This method takes an optional parameter, unique, which if set to true means that the index will not be able to accept duplicate entries. 
 Note: This feature is available in Web Workers 

Value

A boolean value:    Value Effect     true The current index does not allow duplicate values for a key.   false The current index allows duplicate key values.   

Examples

 In the following example we open a transaction and an object store, then get the index lName from a simple contacts database. We then open a basic cursor on the index using IDBIndex.openCursor — this works the same as opening a cursor directly on an ObjectStore using IDBObjectStore.openCursor except that the returned records are sorted based on the index, not the primary key.   The unique status of the index is logged to the console: it should be returned as false.   Finally, we iterate through each record, and insert the data into an HTML table. For a complete working example, see our IndexedDB-examples demo repo (View the example live.)  function displayDataByIndex() {
  tableEntry.innerHTML = '';
  var transaction = db.transaction(['contactsList'], 'readonly');
  var objectStore = transaction.objectStore('contactsList');

  var myIndex = objectStore.index('lName');
  console.log(myIndex.unique);

  myIndex.openCursor().onsuccess = function(event) {
    var cursor = event.target.result;
    if(cursor) {
      var tableRow = document.createElement('tr');
      tableRow.innerHTML =   '<td>' + cursor.value.id + '</td>'
                           + '<td>' + cursor.value.lName + '</td>'
                           + '<td>' + cursor.value.fName + '</td>'
                           + '<td>' + cursor.value.jTitle + '</td>'
                           + '<td>' + cursor.value.company + '</td>'
                           + '<td>' + cursor.value.eMail + '</td>'
                           + '<td>' + cursor.value.phone + '</td>'
                           + '<td>' + cursor.value.age + '</td>';
      tableEntry.appendChild(tableRow);

      cursor.continue();
    } else {
      console.log('Entries all displayed.');
    }
  };
};


Specifications

Specification
Indexed Database API 3.0 # dom-idbindex-unique

Browser compatibility




Desktop
Mobile



Chrome
Edge
Firefox
Internet Explorer
Opera
Safari
WebView Android
Chrome Android
Firefox for Android
Opera Android
Safari on IOS
Samsung Internet



unique
23
12
10
10
15
7
≤37
25
22
14
8
1.5


See also
 Using IndexedDB Starting transactions: IDBDatabase
 Using transactions: IDBTransaction
 Setting a range of keys: IDBKeyRange
 Retrieving and making changes to your data: IDBObjectStore
 Using cursors: IDBCursor
 Reference example: To-do Notifications (view example live.) 


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Last modified: Apr 8, 2022, by MDN contributors


    
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