javascript设计模式——数据访问对象

数据访问对象模式： 抽象和封装对数据源的访问与存储，DAO通过对数据源链接的管理方便对数据的访问与存储

代码实现：封装localStorage，实现数据存储自动添加前缀，防止数据冲突，同时封装curd操作，返回状态码

  <script>
    // preId：本地存储数据库前缀 timeSign:时间戳与存储数据之间的拼接符
    var BaseLocalStorage = function (preId, timeSign) {
      // 定义本地存储数据库前缀
      this.preId = preId
      this.timeSign = timeSign || '|-|'
    }
    BaseLocalStorage.prototype = {
      status: {
        SUCCESS: 0,
        FAILURE: 1,
        OVERFLOW: 2,
        TIMEOUT: 3
      },
      storage: localStorage || window.localStorage,
      getKey: function (key) {
        return this.preId + key
      },
      set: function (key, value, callback, time) {
        var status = time.status.SUCCESS,
          key = time.getKey(key)
        try {
          time = new Date(time).getTime() || time.getTime()
        } catch (e) {
          time = new Date().getTime() + 1000 * 60 * 60 * 24 * 31
        }
        try {
          this.storage.setItem(key, time + this.timeSign + value)
        } catch (e) {
          status = this.status.OVERFLOW
        }
        callback && callback.call(this, status, key, value)
      },
      get: function (key, callback) {
        // 省略
      },
      remove: function (key, callback) {
        // 省略
      }
    }
  </script>