摘要：之前我在開發過程中使用的是，可以直接寫查詢數據。，用鍵值模式存儲數據，而且就是專門為小數量數據設計的。只能是字符串而且空間有限。下面是自己看了阮一峰的文章簡單的學習了下對這個瀏覽器數據庫有個大概的了解，下面是個人對簡單的封裝。

IndexedDB?瀏覽器數據庫，是一個非關系型數據庫，數據形式使用的是json，IndexedDB適合存儲大量數據，它的API是異步調用的，當然他的api?也相對復雜。

當然瀏覽器數據存儲 還有LocalStorage，Cookies，web SQL等 為什么還再來一個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只能是字符串 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也能提供你更為復雜的查詢數據的方式，還能建立索引，他的索引還是挺666的。

下面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 對這個瀏覽器數據庫有個大概的了解，下面是個人對IndexedDB 簡單的封裝。

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

export default {
  // indexedDB兼容
  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("打開數據庫失敗");
    };

    request.onsuccess = function() {
      console.log("打開數據庫成功");
    };
    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
            });
          }
        }
      }
    };
  },
  // 打開數據庫
  openDB: function() {
    return new Promise((resolve, reject) => {
      let request = this.indexedDB.open(dbName, dbVersion);

      request.onerror = function(event) {
        reject("IndexedDB數據庫打開錯誤，" + 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);
    };
  },
  // 關閉數據庫
  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();
  }
};

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此隨筆乃本人學習工作記錄，如有疑問歡迎在下面評論，轉載請標明出處。

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