A small query library for IndexedDB


Query construction
------------------

A query consists of the name of an index, an operation, and a
comparison value. This is how you construct a query:

  Index("make").oneof("BMW", "Volkswagen")

This will return all objects whose "make" index value is
either "BMW" or "Volkswagen". Available operations are:

  * eq
  * lt, lteq
  * gt, gteq
  * between, betweeq
  * oneof

It is possible to link queries with boolean operations, e.g.:

  Index("make").eq("BMW")
    .and(Index("model").eq("325i"))
    .and(Index("year").lteq(1991))


Getting results
---------------

Getting results from a query works very much like getting results from
a single index in IndexedDB. You have the option of a cursor, e.g.:

  let cars = [];
  let store = transaction.objectStore("cars");
  let request = query.openCursor(store);
  request.onsuccess = function (event) {
    let cursor = request.result;
    if (cursor) {
      cars.push(cursor.value);
      cursor.continue();
    }
  }

or simply getting all values at once:

  let cars;
  let request = query.getAll(store);
  request.onsuccess = function (event) {
    cars = request.result;
  }

`query.openKeyCursor` and `query.getAllKeys` are also available if
just the keys are of interest.