derive-schema-from-idb.js

function nameFromKeyPath (keyPath) {
  return typeof keyPath === 'string' ?
    keyPath :
    keyPath ? ('[' + [].join.call(keyPath, '+') + ']') : "";
}

function createTableSchema (
  name,
  primKey,
  indexes
) {
  return {
    name,
    primKey,
    indexes,
    mappedClass: null,
    idxByName: indexes.reduce((result, item, i) => {
        var nameAndValue = [item.name, item]
        if (nameAndValue) result[nameAndValue[0]] = nameAndValue[1];
        return result;
    }, {})
  };
}

function createIndexSpec(
  name,
  keyPath,
  unique,
  multi,
  auto,
  compound,
  isPrimKey
) {
  return {
    name,
    keyPath,
    unique,
    multi,
    auto,
    compound,
    src: (unique && !isPrimKey ? '&' : '') + (multi ? '*' : '') + (auto ? "++" : "") + nameFromKeyPath(keyPath)
  }
}

function buildGlobalSchema(
  db,
  idbdb,
  tmpTrans
) {
  const globalSchema = {};
  const dbStoreNames = Array.from(idbdb.objectStoreNames)
  dbStoreNames.forEach(storeName => {
    const store = tmpTrans.objectStore(storeName);
    let keyPath = store.keyPath;
    const primKey = createIndexSpec(
      nameFromKeyPath(keyPath),
      keyPath || "",
      false,
      false,
      !!store.autoIncrement,
      keyPath && typeof keyPath !== "string",
      true
    );
    const indexes = [];
    for (let j = 0; j < store.indexNames.length; ++j) {
      const idbindex = store.index(store.indexNames[j]);
      keyPath = idbindex.keyPath;
      var index = createIndexSpec(
        idbindex.name,
        keyPath,
        !!idbindex.unique,
        !!idbindex.multiEntry,
        false,
        keyPath && typeof keyPath !== "string",
        false
      );
      indexes.push(index);
    }
    globalSchema[storeName] = createTableSchema(storeName, primKey, indexes);
  });
  return globalSchema;
}

const getDb = () => new Promise(resolve => {
  indexedDB.open('memex').onsuccess = function (event) {
    resolve(event.target.result)
  }
})

async function main() {
  const db = await getDb()
  
  return buildGlobalSchema(storageMan.backend.dexie, db, db.transaction(db.objectStoreNames))
}

main().then(console.log)