index.js

//     express-paginate
//     Copyright (c) 2014- Nick Baugh <niftylettuce@gmail.com> (http://niftylettuce.com)
//     MIT Licensed

// Node.js pagination middleware and view helpers.

// * Author: [@niftylettuce](https://twitter.com/#!/niftylettuce)
// * Source: <https://github.com/niftylettuce/express-paginate>

var qs = require('qs');
var url = require('url');
var assign = require('lodash.assign');
var clone = require('lodash.clone');
var isObject = require('lodash.isobject');
var util = require('util');

exports = module.exports;

exports.href = function href(req) {

  return function(prev, params) {

    var query = clone(req.query);

    if (typeof prev === 'object') {
      params = prev;
      prev = false;
    } else {
      prev = (typeof prev === 'boolean') ? prev : false;
      query.page = parseInt(query.page, 10);
      query.page = prev ? query.page-= 1 : query.page += 1;
      query.page = (query.page < 1) ? 1 : query.page;
    }

    // allow overriding querystring params
    // (useful for sorting and filtering)
    // another alias for `_.assign` is `_.extend`
    if (isObject(params))
      query = assign(query, params);

    return url.parse(req.originalUrl).pathname + '?' + qs.stringify(query);

  };
};

exports.hasNextPages = function hasNextPages(req) {
  return function(pageCount) {
    if (typeof pageCount !== 'number' || pageCount < 0)
      throw new Error('express-paginate: `pageCount` is not a number >= 0');
    return req.query.page < pageCount;
  };
};

exports.getArrayPages = function(req) {
  return function(limit, pageCount, currentPage) {
    var maxPage = pageCount;

    // limit default is 3
    limit = limit || 3;

    if (typeof limit !== 'number' || limit < 0)
      throw new Error('express-paginate: `limit` is not a number >= 0');

    if (typeof pageCount !== 'number' || pageCount < 0)
      throw new Error('express-paginate: `pageCount` is not a number >= 0');

    currentPage = parseInt(currentPage, 10);
    if (Number.isNaN(currentPage) || currentPage < 0)
      throw new Error('express-paginate: `currentPage` is not a number >= 0');

    if (limit > 0) {
      var end = Math.min(Math.max(currentPage + Math.floor(limit / 2), limit), pageCount);
      var start = Math.max(1, (currentPage < (limit - 1)) ? 1 : (end - limit) + 1);

      var pages = [];
      for (var i = start; i <= end; i++) {
        pages.push({
          number: i,
          url: exports.href(req)()
          .replace('page=' + (currentPage + 1), 'page=' + i)
        });
      }

      return pages;
    }
  }
}

exports.middleware = function middleware(limit, maxLimit) {

  var _limit = (typeof limit === 'number') ? parseInt(limit, 10) : 10;

  var _maxLimit = (typeof maxLimit === 'number') ? parseInt(maxLimit, 10) : 50;

  return function _middleware(req, res, next) {

    req.query.page = (typeof req.query.page === 'string') ? parseInt(req.query.page, 10) || 1 : 1;

    req.query.limit = (typeof req.query.limit === 'string') ? parseInt(req.query.limit, 10) || 0 : _limit;

    if (req.query.limit > _maxLimit)
      req.query.limit = _maxLimit;

    if (req.query.page < 1)
      req.query.page = 1;

    if (req.query.limit < 0)
      req.query.limit = 0;

    req.skip = req.offset = (req.query.page * req.query.limit) - req.query.limit;

    res.locals.paginate = {};
    res.locals.paginate.page = req.query.page;
    res.locals.paginate.limit = req.query.limit;
    res.locals.paginate.href = exports.href(req);
    res.locals.paginate.hasPreviousPages = req.query.page > 1;
    res.locals.paginate.hasNextPages = exports.hasNextPages(req);
    res.locals.paginate.getArrayPages = exports.getArrayPages(req);

    next();

  };

};