GUIDES

http://pouchdb.com/guides/

1.建立couchDB环境

• 下载并安装CouchDB：

  https://couchdb.apache.org/#download

• 测试：
  • 于CMD下，执行 curl localhost:5984
  • 打开 http://localhost:5984/_utils/fauxton/ 或 http://localhost:5984/_utils/ 以进入 CouchDB界面
• Set _utilsp CORS （用于跨域）
  • 安装：于CMD下，执行 npm install -g add-cors-to-couchdb
  • 运行：于CMD下，执行 add-cors-to-couchdb

2.建立PouchDB环境

• 下载
  • https://pouchdb.com/download.html
• 在html页面引入
  • <script src="pouchdb-3.4.0.min.js"></script>

3.使用pouchdb数据库

本地数据库

    //创建数据库:var db = new PouchDB('kittens');

远程数据库

    //创建数据库:var db = new PouchDB('http://localhost:5984/kittens');

打开http://localhost:5984/kittens可以预览数据库信息

地址解析:   http://     localhost:5984     /kittens|_____|     |____________|      |_____||              |                |Protocol     Where CouchDB       database(https if    itself is           nameCloudant)    hosted

使用info获取数据库信息

    db.info().then(function (info) {console.log(info);})

删除本地的所有数据库（Chrome）

• 使用ClearBrowserData
• 清除浏览器缓存

4.使用文档数据

文档数据结构：

    SQL concept         PouchDB concepttable       <=>     no equivalent(不存在表格)row         <=>     document(相当于doc)column      <=>     field（值域）primary     <=>     key primary key (_id)index       <=>     view

定义一个doc结构对象，*doc对象必须要有_id属性

    var doc = {"_id": "mittens","name": "Mittens","occupation": "kitten","age": 3,"hobbies": ["playing with balls of yarn","chasing laser pointers","lookin' hella cute"]};

使用put方法存储到数据库

    db.put(doc);

获取数据:（根据_id获取）

    db.get('mittens').then(function (doc) {console.log(doc);});

数据版本 (_rev)

_rev:

• 版本标志位
• 操作数据时，需要设置该属性

更新数据方法:

手动设置该属性

    doc.age = 4;doc._rev = "1-bea5fa18e06522d12026f4aee6b15ee4";//（传入当前的_rev属性）db.put(doc);

获取当前数据，此时即包含_rev属性

    db.get('mittens').then(function (doc) {// update his agedoc.age = 4;// put him backreturn db.put(doc);}).then(function () {// fetch mittens againreturn db.get('mittens');}).then(function (doc) {console.log(doc);});

更新数据时，需要传入当前的_rev属性，若不输入_rev属性，会报错如下：

    {"status": 409,"name": "conflict","message": "Document update conflict"}

5.异步处理数据

callback:

    db.get('mittens', function (error, doc) {if (error) {// oh noes! we got an error} else {// okay, doc contains our document}});

promises:

    db.get('charlie').then(function (charlie) {// Within this function, you can do// try/catch/return like you normally would,// and it will be handled asynchronously!}).then(function (result) {// If the previous function returned something// (or returned undefined), it will show up here // as "result".}).catch(function (err) {// If the previous function threw an error,// it will show up here as "err".});

6.更新删除数据

创建一个默认的doc（若存在则获取，不存在则创建）

    db.get('config').catch(function (err) {if (err.status === 404) { // not found!return {_id: 'config',background: 'blue',foreground: 'white',sparkly: 'false'};} else { // hm, some other errorthrow err;}}).then(function (configDoc) {// sweet, here is our configDoc}).catch(function (err) {// handle any errors});

删除数据

When you remove() a document, it's not really deleted; it just gets a _deleted attribute added to it)

    //1)直接remove docdb.get('mydoc').then(function (doc) {return db.remove(doc);});//2) 使用_id,_revdb.get('mydoc').then(function (doc) {return db.remove(doc._id, doc._rev);});//3) 将_deleted字段设为true  db.get('mydoc').then(function (doc) {doc._deleted = true;return db.put(doc);});

7.Bulk operations (批量操作)

bulkDocs():(批量插入)

    db.bulkDocs([{_id: 'mittens',occupation: 'kitten',cuteness: 9.0},{_id: 'katie',occupation: 'kitten',cuteness: 7.0},{_id: 'felix',occupation: 'kitten',cuteness: 8.0}]);

allDocs() 批量查询

    db.put({_id: new Date().toJSON(),name: 'Mittens',occupation: 'kitten',cuteness: 9.0}).then(function () {return db.put({_id: new Date().toJSON(),name: 'Katie',occupation: 'kitten',cuteness: 7.0});}).then(function () {return db.put({_id: new Date().toJSON(),name: 'Felix',occupation: 'kitten',cuteness: 8.0});]).then(function () {return db.allDocs({include_docs: true});}).then(function (response) {console.log(response);}).catch(function (err) {console.log(err);});

8.使用 attachments

base64:

    btoa('hello world')      <=> "aGVsbG8gd29ybGQ="atob('aGVsbG8gd29ybGQ=') <=> "hello world"

Image attachments

    db.put({_id: 'meowth', _attachments: {'meowth.png': {content_type: 'image/png',data: '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'}}}).then(function () {return db.getAttachment('meowth', 'meowth.png');}).then(function (blob) {var url = URL.createObjectURL(blob);var img = document.createElement('img');img.src = url;document.body.appendChild(img);}).catch(function (err) {console.log(err);});

9.Replication(同步/拷贝 数据)

1.创建本地数据库

    var localDB = new PouchDB('mylocaldb')

2.创建要要远程的数据库

    var remoteDB = new PouchDB('http://localhost:5984/myremotedb')

3.同步本地数据库到远程的数据库

    localDB.replicate.to(remoteDB).on('complete', function () {// yay, we're done!}).on('error', function (err) {// boo, something went wrong!});

4.双向复制

    localDB.replicate.to(remoteDB);localDB.replicate.from(remoteDB);

or

    localDB.sync(remoteDB);localDB.sync(remoteDB).on('complete', function () {// yay, we're in sync!}).on('error', function (err) {// boo, we hit an error!});

5.同步的应答操作

    //1.To enable live replication, you simply specify {live: true}:localDB.sync(remoteDB, {live: true}).on('change', function (change) {// yo, something changed!}).on('error', function (err) {// yo, we got an error! (maybe the user went offline?)})));//2.You can allow PouchDB to automatically handle this error, and retry until the connection is re-established, by using the retry option:localDB.sync(remoteDB, {live: true,retry: true}).on('change', function (change) {// yo, something changed!}).on('paused', function (info) {// replication was paused, usually because of a lost connection}).on('active', function (info) {// replication was resumed}).on('error', function (err) {// totally unhandled error (shouldn't happen)})));

6.取消同步

    //1.var syncHandler = localDB.sync(remoteDB, {live: true,retry: true});syncHandler.on('complete', function (info) {// replication was canceled!});syncHandler.cancel(); // <-- this cancels it//2.var replicationHandler = localDB.replicate.to(remoteDB, {live: true,retry: true});replicationHandler.on('complete', function (info) {// replication was canceled!});replicationHandler.cancel(); // <-- this cancels it

10.Map/reduce queries

临时创建:

    //emit()的内容 是 用于查询时的数据(key对应的字段)//此处的意思就是创建一个index,查找doc.name 为 'foo'的所有数据db.query(function (doc, emit) {emit(doc.name);}, {key: 'foo'}).then(function (result) {// found docs with name === 'foo'}).catch(function (err) {// handle any errors});

持久性创建:

首先创建一个视图(index)

    //注意 _id 命名规范以   _design/  开头var ddoc = {_id: '_design/my_index',views: {//以name为查找的属性by_name: {map: function (doc) { emit(doc.name); }.toString()}}};// save itpouch.put(ddoc).then(function () {// success!}).catch(function (err) {// some error (maybe a 409, because it already exists?)});

然后就可以通过id,视图名直接使用

    //查找name 为test的数据db.query('my_index/by_name',{key:'test'  }).then(function (res) {// got the query results}).catch(function (err) {// some error});//第一次使用的时候因为要创建视图会相对慢，可以先实行一个空的查询让其先建立视图db.query('my_index/by_name', {limit: 0 // don't return any results}).then(function (res) {// index was built!}).catch(function (err) {// some error});

Map functions

    //Map functions:function myMapFunction(doc) {if (doc.type === 'pokemon') {if (doc.name === 'Pikachu') {emit('Pika pi!');} else {emit(doc.name);}}}// find pokemon with name === 'Pika pi!'pouch.query(myMapFunction, {key          : 'Pika pi!', include_docs : true}).then(function (result) {// handle result}).catch(function (err) {// handle errors});// find the first 5 pokemon whose name starts with 'P'pouch.query(myMapFunction, {startkey     : 'P', endkey       : 'P\uffff', limit        : 5, include_docs : true}).then(function (result) {// handle result}).catch(function (err) {// handle errors});//Reduce functions:// emit the first letter of each pokemon's namevar myMapReduceFun = {map: function (doc) {emit(doc.name.charAt(0));},reduce: '_count'};// count the pokemon whose names start with 'P'pouch.query(myMapReduceFun, {key: 'P', reduce: true, group: true}).then(function (result) {// handle result}).catch(function (err) {// handle errors});

11.压缩，删除数据库

Compacting a database

return db.compact().then(function (info) {// compaction complete
}).catch(function (err) {// handle errors
});

Auto-compaction

    var db = new PouchDB('mydb', {auto_compaction: true});

Destroying a database

    PouchDB.destroy('mydb').then(function () {// database destroyed}).catch(function (err) {// error occurred})