Quelle async-storage.js Sprache: JAVA

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/**
*
* Adapted from https://github.com/mozilla-b2g/gaia/blob/f09993563fb5fec4393eb71816ce76cb00463190/shared/js/async_storage.js
* (converted to use Promises instead of callbacks).
*
* This file defines an asynchronous version of the localStorage API, backed by
* an IndexedDB database.  It creates a global asyncStorage object that has
* methods like the localStorage object.
*
* To store a value use setItem:
*
*   asyncStorage.setItem("key", "value");
*
* This returns a promise in case you want confirmation that the value has been stored.
*
*  asyncStorage.setItem("key", "newvalue").then(function() {
*    console.log("new value stored");
*  });
*
* To read a value, call getItem(), but note that you must wait for a promise
* resolution for the value to be retrieved.
*
*  asyncStorage.getItem("key").then(function(value) {
*    console.log("The value of key is:", value);
*  });
*
* Note that unlike localStorage, asyncStorage does not allow you to store and
* retrieve values by setting and querying properties directly. You cannot just
* write asyncStorage.key; you have to explicitly call setItem() or getItem().
*
* removeItem(), clear(), length(), and key() are like the same-named methods of
* localStorage, and all return a promise.
*
* The asynchronous nature of getItem() makes it tricky to retrieve multiple
* values. But unlike localStorage, asyncStorage does not require the values you
* store to be strings.  So if you need to save multiple values and want to
* retrieve them together, in a single asynchronous operation, just group the
* values into a single object. The properties of this object may not include
* DOM elements, but they may include things like Blobs and typed arrays.
*
*/

"use strict";

const DBNAME = "devtools-async-storage";
const DBVERSION = 1;
const STORENAME = "keyvaluepairs";
var db = null;

loader.lazyRequireGetter(
  this,
  "indexedDB",
  "resource://devtools/shared/indexed-db.js"
);

function withStore(type, onsuccess, onerror) {
  if (db) {
    const transaction = db.transaction(STORENAME, type);
    const store = transaction.objectStore(STORENAME);
    onsuccess(store);
  } else {
    const openreq = indexedDB.open(DBNAME, DBVERSION);
    openreq.onerror = function withStoreOnError() {
      onerror();
    };
    openreq.onupgradeneeded = function withStoreOnUpgradeNeeded() {
      // First time setup: create an empty object store
      openreq.result.createObjectStore(STORENAME);
    };
    openreq.onsuccess = function withStoreOnSuccess() {
      db = openreq.result;
      const transaction = db.transaction(STORENAME, type);
      const store = transaction.objectStore(STORENAME);
      onsuccess(store);
    };
  }
}

function getItem(itemKey) {
  return new Promise((resolve, reject) => {
    let req;
    withStore(
      "readonly",
      store => {
        store.transaction.oncomplete = function onComplete() {
          let value = req.result;
          if (value === undefined) {
            value = null;
          }
          resolve(value);
        };
        req = store.get(itemKey);
        req.onerror = function getItemOnError() {
          console.error("Error in asyncStorage.getItem():", req.error.name);
          reject(req.error);
        };
      },
      reject
    );
  });
}

function setItem(itemKey, value) {
  return new Promise((resolve, reject) => {
    withStore(
      "readwrite",
      store => {
        store.transaction.oncomplete = resolve;
        const req = store.put(value, itemKey);
        req.onerror = function setItemOnError() {
          console.error("Error in asyncStorage.setItem():", req.error.name);
          reject(req.error);
        };
      },
      reject
    );
  });
}

function removeItem(itemKey) {
  return new Promise((resolve, reject) => {
    withStore(
      "readwrite",
      store => {
        store.transaction.oncomplete = resolve;
        const req = store.delete(itemKey);
        req.onerror = function removeItemOnError() {
          console.error("Error in asyncStorage.removeItem():", req.error.name);
          reject(req.error);
        };
      },
      reject
    );
  });
}

function clear() {
  return new Promise((resolve, reject) => {
    withStore(
      "readwrite",
      store => {
        store.transaction.oncomplete = resolve;
        const req = store.clear();
        req.onerror = function clearOnError() {
          console.error("Error in asyncStorage.clear():", req.error.name);
          reject(req.error);
        };
      },
      reject
    );
  });
}

function length() {
  return new Promise((resolve, reject) => {
    let req;
    withStore(
      "readonly",
      store => {
        store.transaction.oncomplete = function onComplete() {
          resolve(req.result);
        };
        req = store.count();
        req.onerror = function lengthOnError() {
          console.error("Error in asyncStorage.length():", req.error.name);
          reject(req.error.name);
        };
      },
      reject
    );
  });
}

function key(n) {
  return new Promise((resolve, reject) => {
    if (n < 0) {
      resolve(null);
      return;
    }

    let req;
    withStore(
      "readonly",
      store => {
        store.transaction.oncomplete = function onComplete() {
          const cursor = req.result;
          resolve(cursor ? cursor.key : null);
        };
        let advanced = false;
        req = store.openCursor();
        req.onsuccess = function keyOnSuccess() {
          const cursor = req.result;
          if (!cursor) {
            // this means there weren"t enough keys
            return;
          }
          if (n === 0 || advanced) {
            // Either 1) we have the first key, return it if that's what they
            // wanted, or 2) we"ve got the nth key.
            return;
          }

          // Otherwise, ask the cursor to skip ahead n records
          advanced = true;
          cursor.advance(n);
        };
        req.onerror = function keyOnError() {
          console.error("Error in asyncStorage.key():", req.error.name);
          reject(req.error);
        };
      },
      reject
    );
  });
}

exports.getItem = getItem;
exports.setItem = setItem;
exports.removeItem = removeItem;
exports.clear = clear;
exports.length = length;
exports.key = key;

quality100%

¤ Dauer der Verarbeitung: 0.30 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.