Node JS - Simple Pagination - How to use Middleware in the route?-CodePudding

I'm new to Node and Express. I am currently adding a pagination function to my API. Most of the hard work is done so far, but I can't make it work since I've refactored and made the pagination a function.

Here is my route:

const projects = require('../controllers/project.controller');

module.exports = (app) => {
  var router = require('express').Router();
  // Retrieve all project
  router.get('/', projects.findAll);
};

Here is the middleware:

const paginatedResults = (model) => {
  return (req, res, next) => {
    const page = parseInt(req.query.page);
    const limit = parseInt(req.query.limit);
    const startIndex = (page - 1) * limit;
    const endIndex = page * limit;

    const results = {};
    if (endIndex < model.length) {
      results.next = {
        page: page   1,
        limit: limit,
      };
    }
    if (startIndex > 0) {
      results.previous = {
        page: page - 1,
        limit: limit,
      };
    }
    results.results = model.slice(startIndex, endIndex);
    res.paginatedResults = results;
    next();
  };
};

const pagination = {
  paginatedResults,
};

module.exports = pagination;

Here is my controller:

exports.findAll = (req, res) => {
  Project.find({}, (err, data) => {
    res.send(data);
  });
};

I'm just wondering is there something I should change within the function? Ideally I'd like to be able to use in the route (e.g. router.get('/', [pagination.paginatedResults(Projects), projects.findAll]))

CodePudding user response：

middlewares work one by one. You try to paginate when you have no results to paginate. If you are fine with using helper function, Try something like this.

//route
const projects = require('../controllers/project.controller');

module.exports = (app) => {
  var router = require('express').Router();
  // Retrieve all project
  router.get('/', projects.findAll);
};


// controller
exports.findAll = (req, res) => {
  const mongoQuery = Project.find();
  const result = await paginateQuery(mongoQuery, req.query.page, req.query.limit);
  res.send(result)
};

// helper
const paginateQuery =async (mongoQuery, page, limit) => {
  const skip = page-1
  const  results =await mongoQuery.skip(skip).limit(limt)
  // transform results the way you want and/or build response object
  return results

};