IDBKeyRange

The IDBKeyRange interface of the IndexedDB API represents a continuous interval over some data type that is used for keys. Records can be retrieved from IDBObjectStore and IDBIndex objects using keys or a range of keys. You can limit the range using lower and upper bounds. For example, you can iterate over all values of a key in the value range A–Z.

A key range can be a single value or a range with upper and lower bounds or endpoints. If the key range has both upper and lower bounds, then it is bounded; if it has no bounds, it is unbounded. A bounded key range can either be open (the endpoints are excluded) or closed (the endpoints are included). To retrieve all keys within a certain range, you can use the following code constructs:

A key is in a key range if the following conditions are true:

• The lower value of the key range is one of the following:
  • undefined
  • Less than key value
  • Equal to key value if lowerOpen is false.
• The upper value of the key range is one of the following:
  • undefined
  • Greater than key value
  • Equal to key value if upperOpen is false.

IDBKeyRange.lower Read only

Lower bound of the key range.

IDBKeyRange.upper Read only

Upper bound of the key range.

IDBKeyRange.lowerOpen Read only

Returns false if the lower-bound value is included in the key range.

IDBKeyRange.upperOpen Read only

Returns false if the upper-bound value is included in the key range.

IDBKeyRange.bound()

Creates a new key range with upper and lower bounds.

IDBKeyRange.only()

Creates a new key range containing a single value.

IDBKeyRange.lowerBound()

Creates a new key range with only a lower bound.

IDBKeyRange.upperBound()

Creates a new upper-bound key range.

IDBKeyRange.includes()

Returns a boolean indicating whether a specified key is inside the key range.

The following example illustrates how you'd use a key range. Here we declare a keyRangeValue as a range between values of "A" and "F". We open a transaction (using IDBTransaction) and an object store, and open a cursor with IDBObjectStore.openCursor, declaring keyRangeValue as its optional key range value. This means that the cursor will only retrieve records with keys inside that range. This range includes the values "A" and "F", as we haven't declared that they should be open bounds. If we used IDBKeyRange.bound("A", "F", true, true);, then the range would not include "A" and "F", only the values between them.

function displayData() {
  var keyRangeValue = IDBKeyRange.bound("A", "F");

  var transaction = db.transaction(['fThings'], 'readonly');
  var objectStore = transaction.objectStore('fThings');

  objectStore.openCursor(keyRangeValue).onsuccess = function(event) {
    var cursor = event.target.result;
    if(cursor) {
      var listItem = document.createElement('li');
      listItem.innerHTML = '<strong>' + cursor.value.fThing + '</strong>, ' + cursor.value.fRating;
      list.appendChild(listItem);

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

• 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.)