Managing Product Reviews with JavaScript

Coding Interview Prep for Senior Engineers in JavaScript

Practicing Intermediate Implementation and Data StreamsLesson 1

Lesson 1

Managing Product Reviews with JavaScript

Introduction

Hello, and welcome to today's lesson! Today, we are going to dive into the world of managing product reviews and applying data aggregation in practice. We will start with a relatively simple Starter Task to set up our base and then gradually build up to a more complex solution involving data aggregation. Let's jump in!

Starter Task: Methods and Their Definitions

For our starter task, we will lay the foundation by implementing basic operations for managing product reviews. These are the methods we will need to implement:

addReview(productId, reviewId, reviewText, rating) — adds a review to the product specified by productId. If a review with reviewId already exists, it updates the existing review. The review contains a flagged field which indicates whether the review is marked as inappropriate (by default, this field is set to false). Returns true if the review was added or updated successfully, false otherwise.
getReview(productId, reviewId) — returns the review details (reviewText, rating, and flagged fields) for the review specified by reviewId under the given productId. If the review or product does not exist, returns null.
deleteReview(productId, reviewId) — deletes the review specified by reviewId under the given productId. Returns true if the review was deleted, false otherwise.

Starter Task Implementation

Let's look at the code that implements these functionalities:

JavaScript
1class ReviewManager {
2    constructor() {
3        // Initialize an empty object to store product reviews.
4        this.products = {};
5    }
6
7    addReview(productId, reviewId, reviewText, rating) {
8        // Ensure the rating is between 1 and 5.
9        if (rating < 1 || rating > 5) {
10            return false; // Invalid rating
11        }
12        // If the product doesn't exist, create a new entry for it.
13        if (!this.products[productId]) {
14            this.products[productId] = {};
15        }
16        // Add or update the review for the product.
17        this.products[productId][reviewId] = { text: reviewText, rating: rating, flagged: false };
18        return true;
19    }
20
21    getReview(productId, reviewId) {
22        // Check if the product and review exist.
23        if (this.products[productId] && this.products[productId][reviewId]) {
24            let review = this.products[productId][reviewId];
25            // Return the review details.
26            return { text: review.text, rating: review.rating, flagged: review.flagged };
27        }
28        return null;
29    }
30
31    deleteReview(productId, reviewId) {
32        // Check if the product and review exist.
33        if (this.products[productId] && this.products[productId][reviewId]) {
34            // Delete the specified review.
35            delete this.products[productId][reviewId];
36            // If no reviews are left for the product, remove the product entry.
37            if (Object.keys(this.products[productId]).length === 0) {
38                delete this.products[productId]; // Remove product if no reviews are left
39            }
40            return true;
41        }
42        return false;
43    }
44}
45
46// Instantiate the ReviewManager
47const reviewManager = new ReviewManager();
48
49// Adding some reviews
50reviewManager.addReview("p1", "r1", "Great product!", 5);
51reviewManager.addReview("p1", "r2", "Not bad", 3);
52
53// Testing getReview method
54console.log(reviewManager.getReview("p1", "r1"));  // Expected: { text: "Great product!", rating: 5, flagged: false }
55console.log(reviewManager.getReview("p1", "r3"));  // Expected: null
56
57// Testing deleteReview method
58console.log(reviewManager.deleteReview("p1", "r2"));  // Expected: true
59console.log(reviewManager.getReview("p1", "r2"));  // Expected: null

This code establishes the foundational methods needed for managing product reviews within a ReviewManager class. The addReview method allows for adding a new review or updating an existing one, ensuring each review contains valid rating values between 1 and 5. The getReview method retrieves the review details for a specific product, including the review text and rating, returning null if the product or review doesn't exist. The deleteReview method facilitates the removal of a specific review, and if no reviews are left for a product, the product itself is removed from the product list. Together, these methods form the basic operations required to manage a collection of product reviews efficiently.

Now, let's extend this with new features.

New Task: Advanced Functions and Data Aggregation

With our basic review management system in place, we will now introduce new methods to handle more complex operations, such as flagging inappropriate reviews and aggregating review data for a specific product.

Here are the new methods we will add:

flagReview(productId, reviewId) — This method flags a specific review as inappropriate for a given product. Returns true if the review was successfully flagged, false otherwise.
aggregateReviews(productId) — This method aggregates review data for a given product, providing statistics such as the total number of reviews, the number of flagged reviews, average rating, and review texts excluding flagged ones. If the product does not have any reviews or does not exist, returns null.

Implementation, Step 1: Adding the `flagReview` Method

First, let's add functionality to flag a review:

JavaScript
1class ReviewManager {
2    // Existing methods remain unchanged...
3
4    flagReview(productId, reviewId) {
5        // Check if the product and review exist.
6        if (this.products[productId] && this.products[productId][reviewId]) {
7            // Flag the review as inappropriate.
8            this.products[productId][reviewId].flagged = true;
9            return true;
10        }
11        return false;
12    }
13}
14
15// Instantiate the ReviewManager
16const reviewManager = new ReviewManager();
17
18// Adding some reviews
19reviewManager.addReview("p1", "r1", "Great product!", 5);
20reviewManager.addReview("p1", "r2", "Not bad", 3);
21reviewManager.addReview("p1", "r3", "Terrible", 1);
22
23// Flagging a review
24reviewManager.flagReview("p1", "r3");
25
26// Testing flagReview method
27console.log(reviewManager.getReview("p1", "r3"));  // Expected: { text: "Terrible", rating: 1, flagged: true }

In this step, we are adding the flagReview method to our ReviewManager class. This method enables users to mark a specific review as inappropriate. It checks whether the product and review exist in the dataset, and if they do, it sets the flagged attribute of the review to true. This flagging mechanism is crucial for maintaining the quality and appropriateness of the reviews in the system.

Step 2: Adding the `aggregateReviews` Method

Next, we will implement the method to aggregate reviews:

JavaScript
1class ReviewManager {
2    // Existing methods remain unchanged...
3
4    flagReview(productId, reviewId) {
5        // Check if the product and review exist.
6        if (this.products[productId] && this.products[productId][reviewId]) {
7            // Flag the review as inappropriate.
8            this.products[productId][reviewId].flagged = true;
9            return true;
10        }
11        return false;
12    }
13
14    aggregateReviews(productId) {
15        // Check if the product exists and has reviews.
16        if (!this.products[productId] || Object.keys(this.products[productId]).length === 0) {
17            return null;  // No reviews or product doesn't exist
18        }
19
20        // Initialize aggregation variables.
21        let totalReviews = Object.keys(this.products[productId]).length;
22        let flaggedReviews = 0;
23        let totalRating = 0;
24        let reviewTexts = [];
25
26        // Iterate through the product's reviews.
27        for (let reviewId in this.products[productId]) {
28            let review = this.products[productId][reviewId];
29            if (review.flagged) {
30                flaggedReviews += 1;
31            } else {
32                totalRating += review.rating;
33                reviewTexts.push(review.text);
34            }
35        }
36
37        let averageRating = flaggedReviews === totalReviews ? 0 : totalRating / (totalReviews - flaggedReviews);
38
39        // Return the aggregated review data.
40        return {
41            totalReviews: totalReviews,
42            flaggedReviews: flaggedReviews,
43            averageRating: averageRating,
44            reviewTexts: reviewTexts
45        };
46    }
47}
48
49// Instantiate the ReviewManager
50const reviewManager = new ReviewManager();
51
52// Adding some reviews
53reviewManager.addReview("p1", "r1", "Great product!", 5);
54reviewManager.addReview("p1", "r2", "Not bad", 3);
55reviewManager.addReview("p1", "r3", "Terrible", 1);
56
57// Flagging a review
58reviewManager.flagReview("p1", "r3");
59
60// Testing the aggregation method
61console.log(reviewManager.aggregateReviews("p1"));
62// Expected:
63// {
64//     totalReviews: 3,
65//     flaggedReviews: 1,
66//     averageRating: 4,
67//     reviewTexts: [ "Great product!", "Not bad" ]
68// }

In this step, the aggregateReviews method is added to the ReviewManager class. This method aggregates review data for a given product by calculating various statistics, such as the total number of reviews, the number of flagged reviews, the average rating excluding flagged reviews, and a list of review texts that are not flagged. The method first ensures the product exists and contains reviews. It then iterates through the reviews to collect the necessary data, considering only non-flagged reviews for the average rating and review texts. If all reviews are flagged, the average rating defaults to zero. This aggregation provides a comprehensive overview of a product’s review status, useful for both users and administrators.

Conclusion

Great job! Today, you have learned how to manage product reviews and apply data aggregation in practice. We started with basic operations for adding, retrieving, and deleting reviews. Then, we extended our functionality to include flagging reviews and aggregating review data. This gradual build-up demonstrates how to enhance features incrementally and handle more complex data aggregation tasks.

Feel free to practice solving similar challenges to strengthen your skills further. Keep coding, and see you in the next lesson!

Enjoy this lesson? Now it's time to practice with Cosmo!

Practice is how you turn knowledge into actual skills.