ctx-paginate

Koa pagination middleware and view helpers. Maintained for Forward Email @forwardemail.

Table of Contents

• Install
• Usage
• API
  • paginate.middleware(limit, maxLimit)
  • paginate.href(ctx)
  • paginate.hasPreviousPages
  • paginate.hasNextPages(ctx)
  • paginate.getArrayPages(ctx)
• Example
• License

Install

npm install koa-ctx-paginate

Usage

Import every method:

const paginate = require('koa-ctx-paginate');

Import selective methods:

const { middleware } = require('koa-ctx-paginate');

API

paginate.middleware(limit, maxLimit)

This middleware validates and supplies default values to ctx.paginate.skip (an alias of ctx.paginate.offset, which can be used to skip or offset a number of records for pagination, e.g. with Mongoose you would do Model.find().skip(ctx.paginate.skip)), ctx.query.limit, ctx.query.page, ctx.state.paginate, ctx.state.hasPreviousPages, and ctx.state.hasNextPages.

Arguments

• limit a Number to limit results returned per page (defaults to 10)
• maxLimit a Number to restrict the number of results returned to per page (defaults to 50) – through this, users will not be able to override this limit (e.g. they can't pass ?limit=10000 and crash your server)

paginate.href(ctx)

When you use the paginate middleware, it injects a view helper function called paginate.href as ctx.state.paginate, which you can use in your views for paginated hyperlinks (e.g. as the href in <a>Prev</a> or <a>Next</a>).

By default, the view helper paginate.href is already executed with the inherited ctx variable, therefore it becomes a function capable of returning a String when executed.

When executed with ctx, it will return a function with two optional arguments, prev (Boolean) and params (String).

The argument prev is a Boolean and is completely optional (defaults to false).

The argument params is an Object and is completely optional.

Pass true as the value for prev when you want to create a <button> or <a> that points to the previous page (e.g. it would generate a URL such as the one in the href attribute of <a href="/users?page=1&limit=10">Prev</a> if ctx.query.page is 2).

Pass an object for the value of params when you want to override querystring parameters – such as for filtering and sorting (e.g. it would generate a URL such as the one in the href attribute of <a href="/users?page=1&limit=10&sort=name">Sort By Name</a> if params is equal to { sort: 'name' }.

Note that if you pass only one argument with a type of Object, then it will generate a href with the current page and use the first argument as the value for params. This is useful if you only want to do something like change the filter or sort querystring param, but not increase or decrease the page number.

See the example below for an example of how implementation looks.

Arguments

• ctx (required) – the request object returned from Koa middleware invocation

Returned function arguments when invoked with ctx

• prev (optional) – a Boolean to determine whether or not to increment the hyperlink returned by 1 (e.g. for "Next" page links)
• params (optional) – an Object of querystring parameters that will override the current querystring in ctx.query (note that this will also override the page querystring value if page is present as a key in the params object) (e.g. if you want to make a link that allows the user to change the current querystring to sort by name, you would have params equal to { sort: 'name' })

paginate.hasPreviousPages

When you use the paginate middleware, it injects a view helper Boolean called hasPreviousPages as ctx.state.hasPreviousPages, which you can use in your views for generating pagination <a>'s or <button>'s – this utilizes ctx.query.page > 1 to determine the Boolean's resulting value (representing if the query has a previous page of results)

paginate.hasNextPages(ctx)

When you use the paginate middleware, it injects a view helper function called hasNextPages as ctx.state.hasPreviousPages, which you can use in your views for generating pagination <a>'s or <button>'s – if the function is executed, it returns a Boolean value (representing if the query has another page of results)

By default, the view helper paginate.hasNextPages is already executed with the inherited ctx variable, therefore it becomes a function capable of returning a Boolean when executed.

When executed with ctx, it will return a function that accepts two required arguments called pageCount and resultsCount.

Arguments

• ctx (required) – the request object returned from Koa middleware invocation

Returned function arguments when invoked with ctx

• pageCount (required) – a Number representing the total number of pages for the given query executed on the page

paginate.getArrayPages(ctx)

Get all the page urls with limit.

Arguments

• ctx (required) – the request object returned from Koa middleware invocation

Returned function arguments when invoked with ctx

• limit (optional) – Default: 3, a Number representing the total number of pages for the given query executed on the page.
• pageCount (required) – a Number representing the total number of pages for the given query executed on the page.
• currentPage (required) – a Number representing the current page.

Example

// # app.js

const koa = require('koa');
const Router = require('koa-router');
const paginate = require('koa-ctx-paginate');

// e.g. `Users` is a database model created with Mongoose
const { Users } = require('../models');

const app = koa();
const router = new Router();

// keep this before all routes that will use pagination
app.use(paginate.middleware(10, 50));

// let's get paginated list of users
router.get('/users', async function (ctx, next) {
  try {
    const [ results, itemCount ] = await Promise.all([
      Users.find({}).limit(ctx.query.limit).skip(ctx.paginate.skip).lean().exec(),
      Users.countDocuments({})
    ]);
    const pageCount = Math.ceil(itemCount / ctx.query.limit);
    if (ctx.is('json')) {
      // inspired by Stripe's API response for list objects
      ctx.body = {
        object: 'list',
        has_more: paginate.hasNextPages(ctx)(pageCount),
        data: results
      };
    } else {
      ctx.render('users', {
        users: results,
        pageCount,
        itemCount,
        pages: paginate.getArrayPages(ctx)(3, pageCount, ctx.query.page)
      });
    }
  } catch (err) {
    ctx.throw(err);
  }
});

app.use(router.routes());

app.listen(3000);

//- users.pug

h1 Users

//- this will simply generate a link to sort by name
//- note how we only have to pass the querystring param
//- that we want to modify here, not the entire querystring
a(href=paginate.href({ sort: 'name' })) Sort by name

//- this assumes you have `?age=1` or `?age=-1` in the querystring
//- so this will basically negate the value and give you
//- the opposite sorting order (desc with -1 or asc with 1)
a(href=paginate.href({ sort: req.query.age === '1' ? -1 : 1 })) Sort by age

ul
  each user in users
    li= user.email

include _paginate

Bootstrap 4.x (used by [Lad][]):

//- _paginate.pug

//- Lad
//- <https://lad.js.org>
//-
//- This examples makes use of Bootstrap 4.x pagination classes and is from Lad
//-
if pageCount && pageCount > 0
  nav(aria-label="Page navigation").d-flex.justify-content-center
    ul.pagination
      if paginate.hasPreviousPages
        li.page-item
          a.page-link(href=paginate.href(true), aria-label=t('Previous'))
            span(aria-hidden="true")
              i.fa.fa-angle-double-left
            span.sr-only= t('Previous')
      else
        li.page-item.disabled
          span.page-link(aria-label=t('Previous'))
            span(aria-hidden="true")
              i.fa.fa-angle-double-left
            span.sr-only= t('Previous')
      if pages
        each page in pages
          if page.number === 1 && pageCount === 1
            li.page-item.disabled
              span.page-link= page.number
          else
            if page.number === ctx.query.page
              li.page-item.active
                a.page-link(href=page.url)= page.number
            else
              li.page-item
                a.page-link(href=page.url)= page.number
      if paginate.hasNextPages(pageCount)
        li.page-item
          a.page-link(href=paginate.href({ page: ctx.query.page + 1 }), aria-label=t('Next'))
            span(aria-hidden="true")
              i.fa.fa-angle-double-right
            span.sr-only= t('Next')
      else
        li.page-item.disabled
          span.page-link(aria-label=t('Next'))
            span(aria-hidden="true")
              i.fa.fa-angle-double-right
            span.sr-only= t('Next')

Bootstrap 3.x:

//- _paginate.pug

//- This examples makes use of Bootstrap 3.x pagination classes

if paginate.hasPreviousPages || paginate.hasNextPages(pageCount)
  .navigation.well-sm#pagination
    ul.pager
      if paginate.hasPreviousPages
        li.previous
          a(href=paginate.href(true)).prev
            i.fa.fa-arrow-circle-left
            |  Previous
      if pages
        each page in pages
          a.btn.btn-default(href=page.url)= page.number
      if paginate.hasNextPages(pageCount)
        li.next
          a(href=paginate.href()).next
            | Next 
            i.fa.fa-arrow-circle-right

License

MIT © Forward Email LLC