indexedDB highest keypath

Question

I have a database inside indexedDB filled using an Emberjs adapter. I have set the keypath like this:

this.addModel(App.Device, { keyPath: \'key\' });

Answer 1

Use objectStore.openKeyCursor with the direction "prev":

const openCursorRequest = store.openKeyCursor(null, 'prev')
openCursorRequest.onsuccess = () => {
  const cursor = openCursorRequest.result
  const maxKey = cursor && cursor.key
  // use maxKey...
}

Using Promise:

const getMaxKey = (db, storeName) => new Promise((resolve, reject) => {
  const tx = db.transaction(storeName, 'readonly')
  const store = tx.objectStore(storeName)
  const openCursorRequest = store.openKeyCursor(null, 'prev')
  openCursorRequest.onsuccess = () => {
    const cursor = openCursorRequest.result
    resolve(cursor && cursor.key)
  }
  openCursorRequest.onerror = () => {
    reject(openCursorRequest.error)
  }
})

Answer 2

Here's an IDB pattern for the last entry:

1. Bind your cursor value to the first ID entry. ("0" should do it since keys are lexicographically ordered.) (Original answer linked to question https://stackoverflow.com/a/22812410/317937 which has now been removed)
2. Use a reverse cursor ("prev" or "prevunique" direction depending on your needs)
3. Your next entry will be the last entry (skip() or continue() either should work)