backbone.paginator

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A pageable, drop-in replacement for Backbone.Collection called Backbone.PageableCollection.

Table of Contents

Migrating from Backbone.Paginator 1.0

Backbone.Paginator 2.0 was originally called backbone-pageable, which in turn was inspired by Backbone.Paginator < 1.0 by @addyosmani. The two projects have merged as of May 2014 and backbone-pageable has effectively become Backbone.Paginator 2.0. This guide describes some of the differences and similarities to ease migration.

Package Naming

Backbone.Paginator 2.0 will continue to use the backbone.paginator name for the file, npm and bower packages. In addition, a new component package is also available, also inheriting the backbone.paginator name.

Module Naming

The module exported by the packages will still be called PageableCollection to emphasize the function of this Backbone plugin as a Collection instead of a View.

API Changes

Backbone.Paginator <= 1.0	Backbone.Paginator 2.0
Backbone.Paginator	Backbone.PageableCollection
Backbone.Paginator.requestPager	PageableCollection.extend({mode: "server" | "infinite"})
Backbone.Paginator.clientPager	PageableCollection.extend({mode: "client"})
paginator_core	Override PageableCollection#sync
paginator_ui	state
server_api	queryParams
bootstrap()	new Backbone.PageableCollection([{...}, ...])
parse()	parse(), parseRecords(), parseState(), parseLinks()
goTo()	getPage()
prevPage(), nextPage()	getPreviousPage(), getNextPage()
howManyPer()	setPageSize()
setSort()	setSorting()
*Filter*()	N/A. Implement your own View or use underscore methods on fullCollection
Diacritic plugin	N/A. See above
N/A	getPageByOffSet()
N/A	hasPreviousPage(), hasNextPage()
N/A	switchMode()

Advantages

Supports client-side and server-side operations

You can initialize Backbone.PageableCollection to paginate and/or sort on the client-side, server-side or both.

Infinite paging

Many public APIs like Github or Facebook support infinite paging, Backbone.PageableCollection can handle them easily.

Comes with reasonable defaults

Server API parameters preconfigured to work with most Rails RESTful APIs by default.

Works well with existing server-side APIs

Query parameter mappings are all configurable, and you can use either 0-based or 1-based indices.

Bi-directional event handling

In client-mode, any changes done on one page is immediately reflected on the others with the appropriate events propagated.

100% compatible with existing code

Backbone.PageableCollection is a strict superset of Backbone.Collection and passes its test suite.

Well tested

Comes with 100s of tests in addition to the Backbone.Collection test suite.

Well documented

Use cases and functionality are thoroughly documented.

No surprising behavior

Backbone.PageableCollection performs internal state sanity checks at appropriate times, so it is next to impossible to get into a weird state.

Light-weight

The library is only 4.1KB minified and gzipped.

Playable Demos

The following examples utilizes Backgrid.js to render the collections.

• Server Mode
• Client Mode
• Infinite Mode

Installation

Installing from Component

component install backbone.paginator

Installing from Node.js

npm install backbone.paginator

Installing from Bower

bower install backbone.paginator

Browser

<script src="underscore.js"></script>
<script src="backbone.js"></script>
<script src="backbone.paginator.js"></script>

Getting to the Backbone.PageableCollection Class from Node.js and AMD

var PageableCollection = require("backbone.paginator");

Getting to the Backbone.PageableCollection Class in the Browser

var PageableCollection = Backbone.PageableCollection;

Introduction

Like Backbone.Collection, you can provide a URL endpoint, configure your initial pagination state and server API mapping by extending Backbone.PageableCollection:

var Book = Backbone.Model.extend({});

var Books = Backbone.PageableCollection.extend({
  model: Book,
  url: "api.mybookstore.com/books",

  // Any `state` or `queryParam` you override in a subclass will be merged with
  // the defaults in `Backbone.PageableCollection` 's prototype.
  state: {

    // You can use 0-based or 1-based indices, the default is 1-based.
    // You can set to 0-based by setting ``firstPage`` to 0.
    firstPage: 0,

    // Set this to the initial page index if different from `firstPage`. Can
    // also be 0-based or 1-based.
    currentPage: 2,

    // Required under server-mode
    totalRecords: 200
  },

  // You can configure the mapping from a `Backbone.PageableCollection#state`
  // key to the query string parameters accepted by your server API.
  queryParams: {

    // `Backbone.PageableCollection#queryParams` converts to ruby's
    // will_paginate keys by default.
    currentPage: "current_page",
    pageSize: "page_size"
  }
});

You can initialize state and queryParams from the constructor too:

var Books = Backbone.PageableCollection.extend({
  model: Book,
  url:"api.mybookstore.com/books"
});

var books = new Books([], {

  // All the `state` and `queryParams` key value pairs are merged with
  // the defaults too.
  state: {
    firstPage: 0,
    currentPage: 0
  },

  queryParams: {
    currentPage: "current_page",
    pageSize: "page_size"
  }
});

Adapting to a Server API

To adapt to an existing server API that do not use will_paginate keys, you can configure the queryParams object hash to map state keys to the query parameters your server will accept. Those query parameters will be in the query string of the URL used for fetching. You can also put extra items into queryParams and they will be in the query string as is. Setting null as the value of any mapping will remove it from the query string. Finally, the values in the queryParams can be either a literal value or a parameter-less function that returns a value.

This is a listing of the default state and queryParam values.

state	queryParams
Attribute Value	Attribute Value
============ ===== firstPage 1 lastPage null	============= ============================
currentPage null	currentPage "page"
pageSize 25	pageSize "per_page"
totalPages null	totalPages "total_pages"
totalRecords null	totalRecords "total_entries"
sortKey null	sortKey "sort_by"
order -1	order "order"
	directions { "-1": "asc", "1": "desc" }

You can consult the API documentation for a detailed explanation of these fields.

Fetching Data and Managing States

You can access the pageable collection's internal state by looking at the state object attached to it. This state object, however, is generally read-only after initialization. There are various methods to help you manage this state, you should use them instead of manually modifying it. For the unusual circumstances where you need to modify the state object directly, a sanity check will be performed at the next time you perform any pagination-specific operations to ensure internal state consistency.

Method	Use When
setPageSize	Changing the page size
setSorting	Changing the sorting
switchMode	Switching between modes
state	Need to read the internal state
get*Page	Need to go to a different page
hasPreviousPage, hasNextPage	Check if paging backward or forward is possible

In addition to the above methods, you can also synchronize the state with the server during a fetch. Backbone.PageableCollection overrides the default Backbone.Collection#parse method to support an additional response data structure that contains an object hash of pagination state. The following is a table of the response data structure formats Backbone.PageableCollection accepts.

Without State	With State
[{}, {}, ...]	[{ pagination state }, [{}, {} ...]]

Most of the time, providing something like this in your response is sufficient for updating the pagination state.

[{"total_entries": 100}, [{}, {}, ...]]

Since 1.1.7, customizing parse has been simplified and the default implementation now delegates to two new methods - parseState and parseRecords. You are encouraged to override them instead of parse if it is not clear how to do so. For infinite mode, you should override parseLinks instead of parseState to return an object of links.

See the examples below or the API for details on customizing parseState, parseRecords and parseLinks.

Bootstrapping

Backbone.PageableCollection is 100% compatible with Backbone.Collection 's interface, so you can bootstrap the models and supply a comparator to the constructor just like you are used to:

// Bootstrap with just 1 page of data for server-mode, or all the pages for
// client-mode.
var books = new Books([
  { name: "A Tale of Two Cities" },
  { name: "Lord of the Rings" },
  // ...
], {
  // Paginate and sort on the client side, default is `server`.
  mode: "client",
  // This will maintain the current page in the order the comparator defined
  // on the client-side, regardless of modes.
  comparator: function (model) { return model.get("name"); }
});

Pagination

Server-Mode

Backbone.Pagination defaults to server-mode, which means it only holds one page of data at a time. All of the get*page operations are done by delegating to fetch. They return a jqXHR in this mode.

books.getFirstPage();
books.getPreviousPage();
books.getNextPage();
books.getLastPage();

// All the `get*Page` methods under server-mode delegates to `fetch`, so you
// can attach a callback to the returned `jqXHR` objects' `done` event.
books.getPage(2).done(function () {
  // do something ...
});

All of the get*Page methods accept the same options Backbone.Collection#fetch accepts under server-mode.

Client-Mode

Client-mode is a very convenient mode for paginating a handful of pages entirely on the client side without going through the network page-by-page. This mode is best suited if you only have a small number of pages so sending all of the data to the client is not too time-consuming.

var books = new Books([
  // Bootstrap all the records for all the pages here
], { mode: "client" });

All of the get*Page methods reset the pageable collection's data to the models belonging to the current page and return the collection itself instead of a jqXHR.

// You can immediately operate on the collection without waiting for jQuery to
// call your `done` callback.
var json = JSON.stringify(books.getLastPage());

// You can force a fetch in client-mode to get the most updated data if the
// collection has gone stale.
books.getFirstPage({ fetch: true });

// Do something interesting with books...

Infinite-Mode

Infinite paging mode is a hybrid of server mode and client mode. Once initialized and bootstrapped, paging backwards will be done on the client-side by default while paging forward will be done by fetching.

As before, you can make use of getFirstPage, getPreviousPage, getNextPage, and getLastPage for navigation under infinite-mode. If a page has been fetched, you can use getPage directly with the page number, an error will be thrown if the page has not been fetched yet.

By default, Backbone.PageableCollection parses the response headers to find out what the first, next and prev links are. The parsed links are available in the links field.

var Issues = Backbone.PageableCollection.extend({
  url: "https://api.github.com/repos/documentclound/backbone/issues?state=closed",
  mode: "infinite"

  // Initial pagination states
  state: {
    pageSize: 15,
    sortKey: "updated",
    order: 1
  },

  // You can remap the query parameters from ``state`` keys from the default
  // to those your server supports. Setting ``null`` on queryParams removed them
  // from being appended to the request URLs.
  queryParams: {
    totalPages: null,
    totalRecords: null,
    sortKey: "sort",
    order: "direction",
    directions: {
      "-1": "asc",
      "1": "desc"
    }
  }

});

var issues = new Issues();

issues.getFirstPage().done(function () {
   // do something interesting...
});

If your server API does not return the links using the Link header like Github does, you can subclass Backbone.PageableCollection to override the parseLinks methods to return a links object.

var FBComment = Backbone.Model.extend({});

var FBComments = Backbone.PageableCollection.extend({
  model: FBComment,
  url: "https://graph.facebook.com/A_REALLY_LONG_FACEBOOK_OBJECT_ID",
  mode: "infinite",
  // Set the indices to 0-based for Graph API.
  state: {
    firstPage: 0
  },
  queryParams: {
    pageSize: "limit",
    // Setting a parameter mapping value to null removes it from the query string
    currentPage: null,
    // Any extra query string parameters are sent as is, values can be functions,
    // which will be bound to the pageable collection instance temporarily
    // when called.
    offset: function () { return this.state.currentPage * this.state.pageSize; }
  },
  // Return all the comments for this Facebook object
  parseRecords: function (resp) {
    return resp.comments.data;
  },
  // Facebook's `paging` object is in the exact format
  // `Backbone.PageableCollection` accepts.
  parseLinks: function (resp, xhr) {
    return resp.comments.paging;
  }
});

To act on the newly fetched models under infinite mode, you can listen to the fullCollection reference's add event like you would under client mode, and render the newly fetched models accordingly.

var ToiletPaper = Backbone.View.extend({

  events: {
    "scroll": "fetchSheets"
  },

  initialize: function (options) {
    this.listenTo(this.collection.fullCollection, "add", this.addSheet);
  },

  addSheet: function () {
    // ...
  },

  fetchSheets: function () {
    this.collection.getNextPage();
  },

  // ...

});

var wordsOfTheDay = new Backbone.PageableCollection({
  mode: "infinite",
  // url, initial state, etc...
});

var toiletPaper = new ToiletPaper({collection: wordsOfTheDay});

$("#toilet-paper-dispenser").append(toiletPaper.render().el);

wordsOfTheDay.fetch();

Note:

Don't override parseState or send down a stateful list of records from the server.

Under infinite mode, totalRecords will always equal to the number of models inside fullCollection i.e. fullCollection.length. PagebleCollection will automatically keep all the states consistent. Modifying the state during infinite paging results in undefined behavior. As such, you shouldn't override parseState and should only send down a stateless list of records as described in Fetching Data and Managing States.

Sorting

Sorting has been drastically simplified in the 1.0 release while retaining the full power it had in older versions.

The main way to define a sorting for a pageable collection is to utilize the setSorting method. Given a sortKey and an order, setSorting sets state.sortKey and state.order to the given values. If order is not given, state.order is assumed. By default a comparator is applied to the full collection under client mode. Calling sort on the full collection will then get the entire pageable collection sorted globally. When operating under server or infinite mode, no comparator will be applied to the collection as sorting is assumed to be done on the server by default. Set options.full to false to apply a comparator to the current page under any mode. To sort a pageable collection under infinite mode on the client side, set options.side to "client" will apply a comparator to the full collection.

Setting sortKey to null removes the comparator from both the current page and the full collection.

var books = new Books([
  ...
], {
  mode: "client"
});

// Sets a comparator on `#fullCollection` that sorts the title in ascending
// order
books.setSorting("title");

// Don't forget to call `sort` just like you would on a `Backbone.Collection`
books.fullCollection.sort();

// Clears the comparator
books.setSorting(null);

// Sets a comparator on the current page that sorts the title in descending
// order
books.setSorting("title", 1, {full: false})
books.sort();

books.switchMode("infinite");

// Sorts the books collection under infinite paging mode on the client side
books.setSorting("title", -1, {side: "client"});
books.fullCollection.sort();

books.switchMode("server");

// Sets a comparator on the current page under server mode
books.setSorting("title", {side: "client", full: false});
books.sort();

Manipulation

This is one of the areas where Backbone.PageableCollection truly shines. A Backbone.PageableCollection instance not only can do everything a plain Backbone.Collection can for the current page, in client-mode, it can also synchronize changes and events across all of the pages. For example, you can add or remove a model from either a Backbone.PageableCollection instance, which is holding the current page, or the Backbone.PageableCollection#fullCollection collection, which is a plain Backbone.Collection holding the models for all of the pages, and the pages will all update themselves to maintain within a page size. Any additions, removals, resets, model attribute changes and synchronization actions are communicated between all the pages throughout the two collections.

// The books collection is initialized to start at the first page.
var books = new Books([
  // bootstrap with all of the models for all of the pages here
], {
  mode: "client"
});

// A book is added to the end of the current page, which will overflow to the
// next page and trigger an `add` event on `fullCollection`.
books.push({ name: "The Great Gatsby"});

books.fullCollection.at(books.state.currentPage - 1 * books.state.pageSize).get("name");
>>> "The Great Gatsby"

// Add a new book to the beginning of the first page.
books.fullCollection.unshift({ name: "Oliver Twist" });
books.at(0).get("name");
>>> "Oliver Twist"

API Reference

See here.

FAQ

1. Which package managers does backbone.paginator support?

   bower, npm, CommonJS and AMD and Component.

2. Why doesn't backbone.paginator support filtering?

   Wheels should be reinvented only when they are crooked. backbone.paginator aims to do one thing only and does it well, which is pagination and sorting. Besides, since Backbone.PageableCollection is 100% compatible with Backbone.Collection, you can do filtering fairly easily with Backbone's built-in support for Underscore.js methods.

Legal

Copyright (c) 2012-2014 Jimmy Yuen Ho Wong and contributors

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.