using setTimeout inside a Dexie iteration

Question

I need to iterate IndexedDB table with the Dexie and process each item with some function.

My code is something like that:

var db = new Dexie(dbName);
        db.version(dbVersion).stores({
            smthtbl: '++id, data, creationTime'});

db.smthtbl.each(function (item) {
    return proccessItem(item);
}).then(function() {
    console.log("done");
    return "done"
});


function proccessItem(item) {
    console.log(item.id + " : " + item.data);
};

And I need to set a timeout between iterations so that each next item is displayed through the timeout.

Answer 1

Something like this might work for you.

The iterateWithDelay function below is reusable for any other case where you want to iterate slowly through an array of items. I also made it pass the index and array in, like .map() does. (You could also add a feature to stop iteration if the callback returns a certain value like false, etc.)

Dry-coded, YMMV, etc. :)

const iterateWithDelay = (items, delay, callback) =>
  new Promise(resolve => {
    let index = 0;
    const tick = () => {
      const item = items[index];
      if (!item) {
        resolve();
        return;
      }
      callback(item, index, items);
      index++;
      setTimeout(tick, delay);
    };
    tick();
  });

var db = new Dexie(dbName);
db.version(dbVersion).stores({ smthtbl: "++id, data, creationTime" });

db.smthtbl
  .toArray(items => iterateWithDelay(items, 100, proccessItem))
  .then(() => {
    console.log("done");
    return "done";
  });

function proccessItem(item) {
  console.log(item.id + " : " + item.data);
}