IndexedDB 簡單封裝

IndexedDB 瀏覽器資料庫，是一個非關係型資料庫，數據形式使用的是json，IndexedDB適合存儲大量數據，它的API是非同步調用的，當然他的api 也相對複雜。

當然瀏覽器數據存儲 還有LocalStorage，Cookies，web SQL等 為什麼還再來一個indexedDB。

之前我在開發過程中使用的是web sql，可以直接寫sql查詢數據。

LocalStorage，用key-value鍵值模式存儲數據，而且Localstorage就是專門為小數量數據設計的。

Cookies只能是字元串 而且空間有限。

如果你在實際應用中希望存儲大量數據時，IndexedDB會明顯的更適合，IndexedDB也能提供你更為複雜的查詢數據的方式，還能建立索引，他的索引還是挺666的。

下麵是自己看了阮一峰的 文章 http://www.ruanyifeng.com/blog/2018/07/indexeddb.html

簡單的學習了下 IndexedDB 對這個瀏覽器資料庫有個大概的瞭解，下麵是個人對IndexedDB 簡單的封裝。

const dbName = "test";
const dbVersion = 1;

export default {
  // indexedDB相容
  indexedDB:
    window.indexedDB ||
    window.webkitindexedDB ||
    window.msIndexedDB ||
    window.mozIndexedDB,
  //name:表名  key:主鍵 ,cursorIndex 索引
  store: {
    teacher: {
      name: "teacher",
      key: "id",
      cursorIndex: [{ name: "teachNum", unique: false }]
    },
    student: {
      name: "student",
      key: "id",
      cursorIndex: [{ name: "stuNum", unique: false }]
    }
  },
  async initDB() {
    let that = this;
    let request = this.indexedDB.open(dbName, dbVersion);
    request.onerror = function() {
      console.log("打開資料庫失敗");
    };

    request.onsuccess = function() {
      console.log("打開資料庫成功");
    };
    request.onupgradeneeded = function(event) {
      let db = event.target.result;
      for (var t in that.store) {
        if (!db.objectStoreNames.contains(that.store[t].name)) {
          var objectStore = db.createObjectStore(that.store[t].name, {
            keyPath: that.store[t].key,
            autoIncrement: true
          });
          for (let i = 0; i < that.store[t].cursorIndex.length; i++) {
            const element = that.store[t].cursorIndex[i];
            objectStore.createIndex(element.name, element.name, {
              unique: element.unique
            });
          }
        }
      }
    };
  },
  // 打開資料庫
  openDB: function() {
    return new Promise((resolve, reject) => {
      let request = this.indexedDB.open(dbName, dbVersion);

      request.onerror = function(event) {
        reject("IndexedDB資料庫打開錯誤，" + event);
      };
      request.onsuccess = function(event) {
        resolve(event.target.result);
      };
    });
  },
  // 刪除表
  deleteDB: function(table) {
    let deleteQuest = this.indexedDB.deleteDatabase(table);
    deleteQuest.onerror = function() {
      return Promise.resolve(false);
    };
    deleteQuest.onsuccess = function() {
      return Promise.resolve(true);
    };
  },
  // 關閉資料庫
  closeDB: async function(db) {
    try {
      let d;
      if (!db) {
        d = await this.openDB();
      }
      let closeQuest = d.closeDB();
      return new Promise(resolve => {
        closeQuest.onerror = function() {
          resolve(false);
        };
        closeQuest.onsuccess = function() {
          resolve(true);
        };
      });
    } catch (error) {
      return Promise.resolve(false);
    }
  },
  // 添加數據，add添加新值
  insert: async function(table, data) {
    try {
      let db = await this.openDB();
      let request = db
        .transaction(table.name, "readwrite")
        .objectStore(table.name)
        .add(data);

      return new Promise((resolve, reject) => {
        request.onerror = function() {
          reject("添加數據出錯");
        };
        request.onsuccess = function() {
          resolve(true);
        };
      });
    } catch (error) {
      console.log(error);
      return Promise.resolve(false);
    }
  },
  // 更新
  update: async function(table, data) {
    try {
      let db = await this.openDB();
      let request = db
        .transaction(table.name, "readwrite")
        .objectStore(table.name)
        .put(data);
      return new Promise(resolve => {
        request.onerror = function() {
          resolve(false);
        };
        request.onsuccess = function() {
          resolve(true);
        };
      });
    } catch (error) {
      return Promise.resolve(false);
    }
  },
  // 刪除數據
  delete: async function(table, keyValue) {
    try {
      let db = await this.openDB();
      let request = db
        .transaction(table.name, "readwrite")
        .objectStore(table.name)
        .delete(keyValue);
      return new Promise(resolve => {
        request.onerror = function() {
          resolve(false);
        };
        request.onsuccess = function() {
          resolve(true);
        };
      });
    } catch (error) {
      return Promise.resolve(false);
    }
  },
  // 清空數據
  clear: async function(table) {
    let db = await this.openDB();
    let store = db.transaction(table.name, "readwrite").objectStore(table.name);
    store.clear();
  },
  // 查詢數據 表名 索引值 索引 key  沒有value key為key 而不是索引
  get: async function(table, keyValue, indexCursor) {
    try {
      let db = await this.openDB();
      let store = db
        .transaction(table.name, "readonly")
        .objectStore(table.name);
      let request;
      request = !keyValue
        ? store.openCursor()
        : indexCursor
          ? store.index(indexCursor).get(keyValue)
          : store.get(keyValue);
      let data = [];
      return new Promise(resolve => {
        request.onerror = function() {
          resolve("查詢數據失敗");
        };
        request.onsuccess = function(event) {
          if (!keyValue && !indexCursor) {
            if (event.target.result) {
              data.push(event.target.result.value);
              event.target.result.continue();
            } else {
              resolve(data);
            }
          } else {
            resolve([event.target.result]);
          }
        };
      });
    } catch (error) {
      return Promise.reject(error);
    }
  },
  //   通過游標操作數據, callback中要有游標移動方式
  handleDataByCursor: async function(table, keyRange) {
    try {
      let kRange = keyRange || "";
      let db = await this.openDB();
      let store = db.transaction(table, "readwrite").objectStore(table),
        request;
      request = store.openCursor(kRange);
      return new Promise(resolve => {
        request.onerror = function() {
          resolve("通過游標獲取數據報錯");
        };
        request.onsuccess = function(event) {
          let cursor = event.target.result;
          resolve(cursor);
        };
      });
    } catch (error) {
      return Promise.reject(error);
    }
  },
  // 通過索引游標操作數據, callback中要有游標移動方式
  handleDataByIndex: async function(table, keyRange, sursorIndex) {
    try {
      let kRange = keyRange || "";
      let db = await this.openDB();
      let store = db.transaction(table, "readwrite").objectStore(table),
        request;
      request = store.index(sursorIndex).openCursor(kRange);
      return new Promise(resolve => {
        request.onerror = function() {
          resolve("通過索引游標獲取數據報錯");
        };
        request.onsuccess = function(event) {
          let cursor = event.target.result;
          if (cursor) {
            resolve(cursor);
          }
        };
      });
    } catch (error) {
      return Promise.reject(error);
    }
  },
  // 創建游標索引
  createCursorIndex: async function(table, cursorIndex, unique) {
    var db = await this.openDB();
    let store = db.transaction(table, "readwrite").objectStore(table);
    store.createIndex(cursorIndex, cursorIndex, {
      unique: unique
    });
    return Promise.resolve();
  }
};

此隨筆乃本人學習工作記錄，如有疑問歡迎在下麵評論，轉載請標明出處。

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