基于浏览器端的数据存储方案

客户端存储目前有两个方案比较

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localStorage大家都很常用，这里就不说了，下面和大家说一下indexDB的存储限制和清理机制。

浏览器存储的最大值是动态调整的，基于你的硬盘的大小. 全局限制的大小是硬盘空闲空间的 50%. 在火狐浏览器中, 可以使用Quota Manager内部工具来追踪每个域名使用了多少硬盘空间, 如果需要可以删除它们.

当可用的磁盘填满了，磁盘容量管理器将会根据 LRU 策略清理数据 —— 最近最少使用的数据将会被优先删除，然后是第二个，直到浏览器不再超过限额。

以下是一些常用的开源库，可以帮助我们更好的使用indexDB

1. localForage
   离线存储， 提供强大的API封装IndexedDB,WebSQL,localStorage

localforage.setItem('key', 'value', function (err) {
  // if err is non-null, we got an error
  localforage.getItem('key', function (err, value) {
    // if err is non-null, we got an error. otherwise, value is the value
  });
});

2.Dexie.js
专业封装 IndexedDB

 const db = new Dexie('MyDatabase');

    // Declare tables, IDs and indexes
    db.version(1).stores({
        friends: '++id, name, age'
    });

      // Find some old friends
    await db.friends
        .where('age')
        .above(75)
        .toArray();

    // or make a new one
    await db.friends.add({
        name: 'Camilla',
        age: 25,
        street: 'East 13:th Street',
        picture: await getBlob('camilla.png')
    });

3.zangodb
给HTML5 IndexedDB 封装类似mongodb类似接口, 如果你熟悉mongodb, 那一定会用zangodb

let db = new zango.Db('mydb', { people: ['age'] });
let people = db.collection('people');

let docs = [
    { name: 'Frank', age: 20 },
    { name: 'Thomas', age: 33 },
    { name: 'Todd', age: 33 },
    { name: 'John', age: 28 },
    { name: 'Peter', age: 33 },
    { name: 'George', age: 28 }
];

people.insert(docs).then(() => {
    return people.find({
        name: { $ne: 'John' },
        age: { $gt: 20 }
    }).group({
        _id: { age: '$age' },
        count: { $sum: 1 }
    }).project({
        _id: 0,
        age: '$_id.age'
    }).sort({
        age: -1
    }).forEach(doc => console.log('doc:', doc));
}).catch(error => console.error(error));

4.JsStore
使用类似 sql的接口操作 indexDB

var value = {
    column1: value1,
    column2: value2,
    column3: value3,
    ...
    columnN: valueN
};

connection.insert({
    into: "TABLE_NAME",
    values: [Value], //you can insert multiple values at a time

}).then(function(rowsAffected) {
    if (rowsAffected > 0) {
        alert('Successfully Added');
    }
}).catch(function(error) {
    alert(error.message);
});

5.minimongo
基于localstorage的浏览器端mongodb数据库

// Require minimongo
var minimongo = require("minimongo");

var LocalDb = minimongo.MemoryDb;

// Create local db (in memory database with no backing)
db = new LocalDb();

// Add a collection to the database
db.addCollection("animals");

doc = { species: "dog", name: "Bingo" };

// Always use upsert for both inserts and modifies
db.animals.upsert(doc, function() {
    // Success:

    // Query dog (with no query options beyond a selector)
    db.animals.findOne({ species:"dog" }, {}, function(res) {
        console.log("Dog's name is: " + res.name);
    });
});

6.pouchdb
基于indexDB的CouchDB-style浏览器端数据库

var db = new PouchDB('dbname');

db.put({
  _id: 'dave@gmail.com',
  name: 'David',
  age: 69
});

db.changes().on('change', function() {
  console.log('Ch-Ch-Changes');
});

db.replicate.to('http://example.com/mydb');

7. lowdb
   小型json数据库，浏览器端基于localStorage

import low from 'lowdb'
import LocalStorage from 'lowdb/adapters/LocalStorage'

const adapter = new LocalStorage('db')
const db = low(adapter)

db.defaults({ posts: [] })
  .write()

// Data is automatically saved to localStorage
db.get('posts')
  .push({ title: 'lowdb' })
  .write()