I'm using a cursor with a lower bound range query. I can't find a way to limit the number of objects returned, similar to a "LIMIT n" clause in a databse.

var keyRange = IDBKeyRange.lowerBound('');

Does it not exist ?

I'm using a cursor with a lower bound range query. I can't find a way to limit the number of objects returned, similar to a "LIMIT n" clause in a databse.

var keyRange = IDBKeyRange.lowerBound('');

Does it not exist ?

• javascript
• indexeddb

3 Answers 3

As you're iterating through the results, you can stop at any time. Something like this should work:

var results = [];
var limit = 20;
var i = 0;

objectStore.openCursor().onsuccess = function (event) {
  var cursor = event.target.result;
  if (cursor && i < limit) {
    results.push(cursor.value);
    i += 1;
    cursor.continue();
  }
  else {
    // Do something with results, which has at most 20 entries
    console.log(results);
  }
};

Also, in the special case where you are selecting based on a key that is made up of sequential numbers, you could use a keyRange to explicitly return only a certain range. But that's generally not the case.

An important fix its replace:

if (cursor && i < limit) {

for

if (cursor && results.length < limit) {

Remember that its an async call, and it could be adding elements on "results" at the same time and "i" would not have the proper value.

You can even search by range in indexedDB with IDBKeyRange.bound function

IDBKeyRange.bound(keyValueFrom, keyValueTo, false, true);

You can set the start value, end value and if you should include the start and end value in the returned items. In my case i want the first value of the range, however i want to exclude the last value.

For details of IDBKeyRange please visit the W3C IndexedDB page