TypeError: Cannot read properties of undefined (reading 'query')

Question

My productController.js

const Product = require('../models/product');

const ErrorHandler = require('../utils/errorHandler');
const catchAsyncError = require('../middlewares/catchAsyncErrors');
const APIFeatures = require('../utils/apiFeatures');

// Get all products => /api/v1/products
exports.getProducts = catchAsyncError(async (req, res, next) => {

    const resPerPage = 4;
    const productCount = await Product.countDocuments();

    const apiFeatures = new APIFeatures(Product.find(), req.query)
                        .search()
                        .filter()
                        .pagination(resPerPage)
    const products = await apiFeatures.query;

    res.status(200).json({
        success: true,
        count: products.length,
        message: 'All products fetched from the database successfully.',
        productCount,
        products
    })
}
)

My APIFeatures.js

const { remove } = require("../models/product");

class APIFeatures {
    constructor(query, queryStr) {
        this.query = query;
        this.queryStr = queryStr;
    }

    search() {
        const keyword = this.queryStr.keyword ? {
            name: {
                $regex: this.queryStr.keyword,
                $options: 'i' // Case insensitive option
            }
        } : {}

        this.query = this.query.find({ ...keyword })
        return this;
    }

    filter() {
        const queryCopy = { ...this.queryStr };

        // Remove the fields from the query string
        const removeFields = ['keyword', 'limit', 'page']
        removeFields.forEach(el => delete queryCopy[el]);

        // Advanced filtering
        let queryStr = JSON.stringify(queryCopy);
        queryStr = queryStr.replace(/\b(gt|gte|lt|lte|in)\b/g, match => `$${match}`);

        this.query = this.query.find(JSON.parse(queryStr));
        return this;
    }

    pagination(resPerPage) {
        const currentPage = Number(this.queryStr.page) || 1;
        const skip = resPerPage * (currentPage - 1);

        this.query = this.query.limit(resPerPage).skip(skip)
    }
}

module.exports = APIFeatures; 

There's a problem with getting all products. Getting single product works fine so I removed that part of the code. The problem is with the query.

I have 2 sample product in my database and it was working fine. I didn't make changes this file but I can't fetch all products using postman.

  const products = await apiFeatures.query;

Answer 1

The error here was pagination I simply solve that by replacing

this.query = this.query.limit(resPerPage).skip(skip);
return this;