10 Node Frameworks to Use in 2019

10 Node Frameworks to Use in 2019

There are many popular Node frameworks to use in 2019. Let's take a look at 10 of them to use for your next project.

There are many popular Node frameworks to use in 2019. Let's take a look at 10 of them to use for your next project.

More developers have switched to using JavaScript to build more applications, especially for the web. This has brought about an exponential growth in the usage of frameworks built specifically for the JavaScript community to facilitate quick prototyping and building of awesome projects.


Table of Contents

More developers have switched to using JavaScript to build more applications, especially for the web. This has brought about an exponential growth in the usage of frameworks built specifically for the JavaScript community to facilitate quick prototyping and building of awesome projects.

When Node.js was introduced to the tech community in 2009 as a tool for building scalable server-side web applications, it came with a lot of benefits which includes but not limited to the usage of event-driven non-blocking input/output model, single-threaded asynchronous programming amongst others.

The fact that, as a developer, you can easily use the same language both for the client-side and server-side scripting easily increased the quick adoption and rapid the usage of Node.
Over the years, a lot of experienced JavaScript developers have built quite a number of impressive frameworks to easily get started with Node.js when developing web applications.

As we look into 2019, I will list some of the most popular Node.js frameworks that you should consider using for building web applications irrespective of the size.

What is a Node framework?

A Node.js framework is just some abstract design, built out of Node.js, that embodies the control flow of the given framework’s design. So it is almost like the skeleton of a program whereby the customised codes you write kind of makes up as the meat that completes the program.

So for every Node.js function, there would be some generic implementation unique to the framework which would then require the user to follow the lead of the framework by adding more codes to define its use case.

Benefits of Node frameworks

Node.js frameworks are mostly used because of their productivity, scalability and speed, making them one of the first choice for building enterprise applications for companies.

Node.js allows you to write the same language for both your front-end and backend, saving you the stress of learning a new language for some simple implementation, and also helping you maintain the same coding pattern all through.

By using a framework, you can work with a set of tools, guidelines, and recommended practices that help you save time. It also can help solidify the code standards across a team of developers.

Selecting a Node Framework

Selecting a framework can be a bit tricky and subjective to its use case. This is because we choose based on a particular feature we like. Ranging from the weight of the framework on the application, speed, simplicity, learning curve, flexibility and configuration, use case or maybe even popularity in some cases, GitHub stars.

Next, lets take a deep dive into the objective of this post and go through the list of Node.js frameworks that will help boost your productivity when building JavaScript applications, especially on the server-side.

1. AdonisJs [GitHub Stars: 5,053]

AdonisJsis a Node.js framework. From the official documentation, “AdonisJs is a Node.js MVC framework that runs on all major operating systems. It offers a stable ecosystem to write a server-side web application so that you can focus on business needs over finalising which package to choose or not.”

The fact that, as a developer, you can easily use the same language both for the client-side and server-side scripting easily increased the quick adoption and rapid the usage of Node.
“We’re big fans of Laravel’s approach (Scotch is built on Laravel) so when we saw those same principles come to the Node side, we were very excited.” - Chris Sevilleja

Why AdonisJS?

AdonisJs has a support for an ORM is made with SQL-databases in mind (PostgreSQL). It creates efficient SQL-queries and is based on active record idea. Its query builder is easy to learn and allows us to build simple queries quickly.

AdonisJs has good support for No-SQL database like MongoDB too. It’s MVC structure is quite similar to Laravel, so if you’ve been using Laravel for web development, AdonisJs will be a walk in the park.

To get started easily check out this comprehensive article by Chimezie here on scotch.io.

2. Express.js [GitHub Stars: 41,036]

Express.js is a fast, non-opinionated, minimalist web framework for Node.js. It is simply a technology built on Node.js which behaves like a middleware to help manage our servers and routes. Looking at the asynchronous nature of Node.js and the fact that Express.js was built on node, the ability to build a light-weight application that can process more than a single request seamlessly actually depends on the serving capability of technologies like express.

It’s robust API allows users to configure routes to send/receive requests between the front-end and the database (acting as a HTTP server framework). A good advantage with express is how it supports a lot of other packages and other template engines such as Pug, Mustache, EJS and a lot more.

Some of the numerous advantages of Express.js includes:

Express.js has shown, over time, that it’s popularity is worth the hype with its easy to use methods and functions. It is probably the most popular Node.js framework available for the JavaScript community on GitHub with over 41,000 stars [Github stars: 41,036].

Looking at this framework and all it’s exciting abilities, I do not see it going away anytime soon.

3. Meteor.js [GitHub Stars: 40,490]

The Meteor docs defines meteor as a full-stack JavaScript platform for developing modern web and mobile applications. It’s major advantage is it’s realtime update. As changes are made to the web app, it automatically updates the template with the latest changes.

The Node.js framework makes development quite very simplified by providing a platform for the entire tier of the application to be in the same language; JavaScript. Making it function just as efficient in both the server and client side.

Meteor stands the capability of serving large projects like reaction commerce( known to be one of the largest and most popular e-commerce open source projects).

The most fascinating aspect of the Meteor framework is the very rich and organised documentation/large community it has, helping users learn fast by reaching out and getting their hands dirty with projects, very fast.

With the fact that meteor is leveraging on the Facebook GraphQL datastack to come up with meteor Apollo, as far back as 2016, only indicates that they have good plans and a visionary perception of what the future holds for data, how it is managed and how it flows. If there is any list of Node.js frameworks to watch out for, I would probably be arrested if I did not add Meteor to that list.

4. Nest.js [GitHub Stars: 10,128]

NestJs is a framework built with Node.js, It is used for building efficient, scalable Node.js server-side applications. Nest uses progressive JavaScript and is written with TypeScript. Being built with TypeScript means that Nest comes with strong typing and combines elements of OOP(Object Oriented Programming), FP(Functional Programming) and FRP(Functional Reactive Programming).

Nest also makes use of Express, It provides an out of the box application architecture which allows for the effortless creation of highly testable, scalable, loosely coupled, and easily maintainable applications.

Nest CLI can be used to generate nest.js applications with a lot of features out of the box. According to the information on the website, one can contact the nest community of developers behind the nest framework to find out more about expertise consulting, on-site enterprise support, trainings, and private sessions. Isn’t that cool? Well I guess it is, and I also think this also should make it into the list of Node.js frameworks to look out for in 2019.

5. Sails.js [GitHub Stars: 19,887]

According to the official site, Sails is another Node.js framework used to build custom enterprise-grade Node.js apps. It boasts of being the most popular MVC Node.js framework with the support for modern apps requirements. The APIs are data-driven, with a scalable service oriented architecture.

Let us take a closer look at what they mean here. Sails bundles an ORM, waterlines, that makes compatibility possible with almost all databases, going as far as providing a huge number of community projects. Some of its officially supported adapters include MYSQL, Mongo, PostgreSQL, Redis, and even Local Disk.

Looking at the backend, Just by running an installation command, sails generate api bookstore for instance, sails blows your mind by providing you some basic blueprints, without you writing any codes at all.

This command provides you endpoints to CRUD bookstore. You think that is all right, check this out: Sails is also compatible with almost all frontend technologies ranging from React, Angular, Backbone, iOS/objective C, Android/java, windows phone and probably even some technologies yet to be created. For this one, 2019 it is! summarised features include:

6. Koa.js [GitHub Stars: 23,902]

Referred to as the next generation web framework for Node.js(according to the website), Koa was created by the same team that created Express.js, making it seem like it would pick up from where express left off. Koa is unique in the fact that it uses some really cool ECMAScript(ES6) methods that have not even landed in some browsers yet, it allows you to work without callbacks, while also providing you with an immense increase in error handling. it requires a Node.js version of at least 0.11 or higher.

According to the website, Koa does not bundle any middleware within core, meaning the middlewares are more cascaded/streamlined, and every line of code is quite elegant and granular, thereby allowing you to structure the parts however you want(component-based middlewares). This makes the framework to have more control over configurations and handling.

Koa became futureproof owing to the fact that it could actually ditch the holy grail of asynchronous functionality: callbacks.

Some key features include:

This is definitely a framework for the future and I am almost beginning to see that if an article for frameworks to lookout for in the year 2020 comes out, it would still probably make the list.

7. LoopBack.js [GitHub Stars: 11,985]

LoopBack is another Node.js framework with an easy-to-use CLI and a dynamic API explorer. It allows you to create your models based on your schema or dynamic models in the absence of a schema. It is compatible with a good number of REST services and a wide variety of databases including MySQL, Oracle, MongoDB, Postgres and so on.

It has the ability to allow a user build a server API that maps to another server, almost like creating an API that is a proxy for another API. It’s support for native mobile and browser SDKs for clients like Android/Java, iOS, Browser javaScript(Angular).

Key features:

Most of these details were collected from their Website/documentation which I found very exciting to go through and even try to get a basic setup up, Indicating that they have a well structured documentation and a community distributed across different media( StrongLoop blog, LoopBack Google Group, LoopBack Gitter channel ). For instance, the Loopback blog provides lots of tutorials and use cases on how to leverage the use of the technology in different ways.

Amongst some of its powerful users are Go Daddy, Flight Office, Bank of America(Meryll Linch), Symantec, Intellum, ShoppinPal and so on.

8. Hapi.js [GitHub Stars: 10,371]

Just like ExpressJs, the common hapi.js(supported by Walmart Labs) is a Node.js framework that helps serve data by intermediating between the server side and client. It is quite a good substitute for Express(they both have their unique features).

Hapi is a configuration-driven pattern, traditionally modeled to control web server operations. A unique feature it has is the ability to create a server on a specific IP, with features like the ‘onPreHandler’, we can do something with a request before it is completed by intercepting it and doing some pre-processing on the request.

Considering it’s ‘handler’ function where we can call a route and still pass some configurations while making the requests, just to get the function to do something specified in the configuration. This handler, from what we see, acts like a pseudo-middleware.

Let us look at some key features that make hapiJs promising:

HapiJs might not be as popular [github stars: 10,371] as Express but it has some good backing up and it seems to be gaining some grounds too. It does not seem like it is slowing down its mark and relevance anytime soon.

9. Derby.js [4,350]

According to the Derby.js site, it is a full stack Node.js framework for writing modern web applications. Derby has been around a little while, quite long enough to have proven itself to hop into 2019 and rock some chords. Let’s see what we have here.

DerbyJs provides you with seamless data synchronisation between your server and client with an automatic conflict resolution powered by ShareDB’s operational transformation of JSON and text. It permits you the opportunity to add customised codes to build highly efficient web applications.

10. Total.js [Github stars: 3,853]

Total.js boast of being a very fast development Node.js framework, that requires little maintenance, with a good performance and a seamless scaling transition. It shows some promise by giving some insight on their website, where they ask for visitors willing to contribute to the growth of the framework. So far the Total.js team has spent some time trying to get more premium sponsors to join them. This is another indication that they have plans to expand and should be checked out for more growth in the nearest future to come.

Total.js has some really beautiful versions like the Total.js Eshop, which contains a user interface optimized for mobile devices, and downloadable by all premium members. The Eshop is one of the best Node.js e-commerce system. This is because of its many versions of unique content management system(CMS).


If there is anything we can pick from this article, I can bet you must have noticed before now that picking a framework is based on what you actually want to achieve with it.

The Node.js frameworks above have purely shown us that whatever framework we are going for, there is an open and welcoming community out there solving issues and ready to aid you with learning the basics of that particular framework, which a is vital factor to look out for amongst lots more other factors like GitHub contributions, stars, issues and so on. Just for the fun of it, you can find a lot more of Node.js frameworks here.

Please note that all the Node.js framework highlighted in this post were selected based on popularity in the JavaScript community, usage and personal opinion.

Do you know of any other awesome Node.js framework that you feel its worthy of being added to the list? please feel free to mention it in the comment section below.

I do hope you find this post very helpful. Happy coding.

How to Use Express.js, Node.js and MongoDB.js

How to Use Express.js, Node.js and MongoDB.js

In this post, I will show you how to use Express.js, Node.js and MongoDB.js. We will be creating a very simple Node application, that will allow users to input data that they want to store in a MongoDB database. It will also show all items that have been entered into the database.

In this post, I will show you how to use Express.js, Node.js and MongoDB.js. We will be creating a very simple Node application, that will allow users to input data that they want to store in a MongoDB database. It will also show all items that have been entered into the database.

Creating a Node Application

To get started I would recommend creating a new database that will contain our application. For this demo I am creating a directory called node-demo. After creating the directory you will need to change into that directory.

mkdir node-demo
cd node-demo

Once we are in the directory we will need to create an application and we can do this by running the command
npm init

This will ask you a series of questions. Here are the answers I gave to the prompts.

The first step is to create a file that will contain our code for our Node.js server.

touch app.js

In our app.js we are going to add the following code to build a very simple Node.js Application.

var express = require("express");
var app = express();
var port = 3000;
app.get("/", (req, res) => {
  res.send("Hello World");
app.listen(port, () => {
  console.log("Server listening on port " + port);

What the code does is require the express.js application. It then creates app by calling express. We define our port to be 3000.

The app.use line will listen to requests from the browser and will return the text “Hello World” back to the browser.

The last line actually starts the server and tells it to listen on port 3000.

Installing Express

Our app.js required the Express.js module. We need to install express in order for this to work properly. Go to your terminal and enter this command.

npm install express --save

This command will install the express module into our package.json. The module is installed as a dependency in our package.json as shown below.

To test our application you can go to the terminal and enter the command

node app.js

Open up a browser and navigate to the url http://localhost:3000

You will see the following in your browser

Creating Website to Save Data to MongoDB Database

Instead of showing the text “Hello World” when people view your application, what we want to do is to show a place for user to save data to the database.

We are going to allow users to enter a first name and a last name that we will be saving in the database.

To do this we will need to create a basic HTML file. In your terminal enter the following command to create an index.html file.

touch index.html

In our index.html file we will be creating an input filed where users can input data that they want to have stored in the database. We will also need a button for users to click on that will add the data to the database.

Here is what our index.html file looks like.

<!DOCTYPE html>
    <title>Intro to Node and MongoDB<title>

    <h1>Into to Node and MongoDB<&#47;h1>
    <form method="post" action="/addname">
      <label>Enter Your Name<&#47;label><br>
      <input type="text" name="firstName" placeholder="Enter first name..." required>
      <input type="text" name="lastName" placeholder="Enter last name..." required>
      <input type="submit" value="Add Name">

If you are familiar with HTML, you will not find anything unusual in our code for our index.html file. We are creating a form where users can input their first name and last name and then click an “Add Name” button.

The form will do a post call to the /addname endpoint. We will be talking about endpoints and post later in this tutorial.

Displaying our Website to Users

We were previously displaying the text “Hello World” to users when they visited our website. Now we want to display our html file that we created. To do this we will need to change the app.use line our our app.js file.

We will be using the sendFile command to show the index.html file. We will need to tell the server exactly where to find the index.html file. We can do that by using a node global call __dirname. The __dirname will provide the current directly where the command was run. We will then append the path to our index.html file.

The app.use lines will need to be changed to
app.use("/", (req, res) => {   res.sendFile(__dirname + "/index.html"); });

Once you have saved your app.js file, we can test it by going to terminal and running node app.js

Open your browser and navigate to “http://localhost:3000”. You will see the following

Connecting to the Database

Now we need to add our database to the application. We will be connecting to a MongoDB database. I am assuming that you already have MongoDB installed and running on your computer.

To connect to the MongoDB database we are going to use a module called Mongoose. We will need to install mongoose module just like we did with express. Go to your terminal and enter the following command.
npm install mongoose --save

This will install the mongoose model and add it as a dependency in our package.json.

Connecting to the Database

Now that we have the mongoose module installed, we need to connect to the database in our app.js file. MongoDB, by default, runs on port 27017. You connect to the database by telling it the location of the database and the name of the database.

In our app.js file after the line for the port and before the app.use line, enter the following two lines to get access to mongoose and to connect to the database. For the database, I am going to use “node-demo”.

var mongoose = require("mongoose"); mongoose.Promise = global.Promise; mongoose.connect("mongodb://localhost:27017/node-demo");

Creating a Database Schema

Once the user enters data in the input field and clicks the add button, we want the contents of the input field to be stored in the database. In order to know the format of the data in the database, we need to have a Schema.

For this tutorial, we will need a very simple Schema that has only two fields. I am going to call the field firstName and lastName. The data stored in both fields will be a String.

After connecting to the database in our app.js we need to define our Schema. Here are the lines you need to add to the app.js.
var nameSchema = new mongoose.Schema({   firstName: String,   lastNameName: String });

Once we have built our Schema, we need to create a model from it. I am going to call my model “DataInput”. Here is the line you will add next to create our mode.
var User = mongoose.model("User", nameSchema);

Creating RESTful API

Now that we have a connection to our database, we need to create the mechanism by which data will be added to the database. This is done through our REST API. We will need to create an endpoint that will be used to send data to our server. Once the server receives this data then it will store the data in the database.

An endpoint is a route that our server will be listening to to get data from the browser. We already have one route that we have created already in the application and that is the route that is listening at the endpoint “/” which is the homepage of our application.

HTTP Verbs in a REST API

The communication between the client(the browser) and the server is done through an HTTP verb. The most common HTTP verbs are

The following table explains what each HTTP verb does.

HTTP Verb Operation
GET Read
POST Create
PUT Update

As you can see from these verbs, they form the basis of CRUD operations that I talked about previously.

Building a CRUD endpoint

If you remember, the form in our index.html file used a post method to call this endpoint. We will now create this endpoint.

In our previous endpoint we used a “GET” http verb to display the index.html file. We are going to do something very similar but instead of using “GET”, we are going to use “POST”. To get started this is what the framework of our endpoint will look like.

app.post("/addname", (req, res) => {
Express Middleware

To fill out the contents of our endpoint, we want to store the firstName and lastName entered by the user into the database. The values for firstName and lastName are in the body of the request that we send to the server. We want to capture that data, convert it to JSON and store it into the database.

Express.js version 4 removed all middleware. To parse the data in the body we will need to add middleware into our application to provide this functionality. We will be using the body-parser module. We need to install it, so in your terminal window enter the following command.

npm install body-parser --save

Once it is installed, we will need to require this module and configure it. The configuration will allow us to pass the data for firstName and lastName in the body to the server. It can also convert that data into JSON format. This will be handy because we can take this formatted data and save it directly into our database.

To add the body-parser middleware to our application and configure it, we can add the following lines directly after the line that sets our port.

var bodyParser = require('body-parser');
app.use(bodyParser.urlencoded({ extended: true }));
Saving data to database

Mongoose provides a save function that will take a JSON object and store it in the database. Our body-parser middleware, will convert the user’s input into the JSON format for us.

To save the data into the database, we need to create a new instance of our model that we created early. We will pass into this instance the user’s input. Once we have it then we just need to enter the command “save”.

Mongoose will return a promise on a save to the database. A promise is what is returned when the save to the database completes. This save will either finish successfully or it will fail. A promise provides two methods that will handle both of these scenarios.

If this save to the database was successful it will return to the .then segment of the promise. In this case we want to send text back the user to let them know the data was saved to the database.

If it fails it will return to the .catch segment of the promise. In this case, we want to send text back to the user telling them the data was not saved to the database. It is best practice to also change the statusCode that is returned from the default 200 to a 400. A 400 statusCode signifies that the operation failed.

Now putting all of this together here is what our final endpoint will look like.

app.post("/addname", (req, res) => {
  var myData = new User(req.body);
    .then(item => {
      res.send("item saved to database");
    .catch(err => {
      res.status(400).send("unable to save to database");
Testing our code

Save your code. Go to your terminal and enter the command node app.js to start our server. Open up your browser and navigate to the URL “http://localhost:3000”. You will see our index.html file displayed to you.

Make sure you have mongo running.

Enter your first name and last name in the input fields and then click the “Add Name” button. You should get back text that says the name has been saved to the database like below.

Access to Code

The final version of the code is available in my Github repo. To access the code click here. Thank you for reading !

Node.js for Beginners - Learn Node.js from Scratch (Step by Step)

Node.js for Beginners - Learn Node.js from Scratch (Step by Step)

Node.js for Beginners - Learn Node.js from Scratch (Step by Step) - Learn the basics of Node.js. This Node.js tutorial will guide you step by step so that you will learn basics and theory of every part. Learn to use Node.js like a professional. You’ll learn: Basic Of Node, Modules, NPM In Node, Event, Email, Uploading File, Advance Of Node.

Node.js for Beginners

Learn Node.js from Scratch (Step by Step)

Welcome to my course "Node.js for Beginners - Learn Node.js from Scratch". This course will guide you step by step so that you will learn basics and theory of every part. This course contain hands on example so that you can understand coding in Node.js better. If you have no previous knowledge or experience in Node.js, you will like that the course begins with Node.js basics. otherwise if you have few experience in programming in Node.js, this course can help you learn some new information . This course contain hands on practical examples without neglecting theory and basics. Learn to use Node.js like a professional. This comprehensive course will allow to work on the real world as an expert!
What you’ll learn:

  • Basic Of Node
  • Modules
  • NPM In Node
  • Event
  • Email
  • Uploading File
  • Advance Of Node

Top 7 Most Popular Node.js Frameworks You Should Know

Top 7 Most Popular Node.js Frameworks You Should Know

Node.js is an open-source, cross-platform, runtime environment that allows developers to run JavaScript outside of a browser. In this post, you'll see top 7 of the most popular Node frameworks at this point in time (ranked from high to low by GitHub stars).

Node.js is an open-source, cross-platform, runtime environment that allows developers to run JavaScript outside of a browser.

One of the main advantages of Node is that it enables developers to use JavaScript on both the front-end and the back-end of an application. This not only makes the source code of any app cleaner and more consistent, but it significantly speeds up app development too, as developers only need to use one language.

Node is fast, scalable, and easy to get started with. Its default package manager is npm, which means it also sports the largest ecosystem of open-source libraries. Node is used by companies such as NASA, Uber, Netflix, and Walmart.

But Node doesn't come alone. It comes with a plethora of frameworks. A Node framework can be pictured as the external scaffolding that you can build your app in. These frameworks are built on top of Node and extend the technology's functionality, mostly by making apps easier to prototype and develop, while also making them faster and more scalable.

Below are 7of the most popular Node frameworks at this point in time (ranked from high to low by GitHub stars).


With over 43,000 GitHub stars, Express is the most popular Node framework. It brands itself as a fast, unopinionated, and minimalist framework. Express acts as middleware: it helps set up and configure routes to send and receive requests between the front-end and the database of an app.

Express provides lightweight, powerful tools for HTTP servers. It's a great framework for single-page apps, websites, hybrids, or public HTTP APIs. It supports over fourteen different template engines, so developers aren't forced into any specific ORM.


Meteor is a full-stack JavaScript platform. It allows developers to build real-time web apps, i.e. apps where code changes are pushed to all browsers and devices in real-time. Additionally, servers send data over the wire, instead of HTML. The client renders the data.

The project has over 41,000 GitHub stars and is built to power large projects. Meteor is used by companies such as Mazda, Honeywell, Qualcomm, and IKEA. It has excellent documentation and a strong community behind it.


Koa is built by the same team that built Express. It uses ES6 methods that allow developers to work without callbacks. Developers also have more control over error-handling. Koa has no middleware within its core, which means that developers have more control over configuration, but which means that traditional Node middleware (e.g. req, res, next) won't work with Koa.

Koa already has over 26,000 GitHub stars. The Express developers built Koa because they wanted a lighter framework that was more expressive and more robust than Express. You can find out more about the differences between Koa and Express here.


Sails is a real-time, MVC framework for Node that's built on Express. It supports auto-generated REST APIs and comes with an easy WebSocket integration.

The project has over 20,000 stars on GitHub and is compatible with almost all databases (MySQL, MongoDB, PostgreSQL, Redis). It's also compatible with most front-end technologies (Angular, iOS, Android, React, and even Windows Phone).


Nest has over 15,000 GitHub stars. It uses progressive JavaScript and is built with TypeScript, which means it comes with strong typing. It combines elements of object-oriented programming, functional programming, and functional reactive programming.

Nest is packaged in such a way it serves as a complete development kit for writing enterprise-level apps. The framework uses Express, but is compatible with a wide range of other libraries.


LoopBack is a framework that allows developers to quickly create REST APIs. It has an easy-to-use CLI wizard and allows developers to create models either on their schema or dynamically. It also has a built-in API explorer.

LoopBack has over 12,000 GitHub stars and is used by companies such as GoDaddy, Symantec, and the Bank of America. It's compatible with many REST services and a wide variety of databases (MongoDB, Oracle, MySQL, PostgreSQL).


Similar to Express, hapi serves data by intermediating between server-side and client-side. As such, it's can serve as a substitute for Express. Hapi allows developers to focus on writing reusable app logic in a modular and prescriptive fashion.

The project has over 11,000 GitHub stars. It has built-in support for input validation, caching, authentication, and more. Hapi was originally developed to handle all of Walmart's mobile traffic during Black Friday.