Tracking Cryptocurrencies via SMS Alarms using JavaScript, Node.js and Twilio

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Bitcoin, Ethereum, Ripple, Bitcoin Cash, Dogecoin, Litecoin—the list of cryptocurrency coins is endless, and new technologies are emerging daily. In this tutorial, we are going to create an app that sends SMS text messages whenever a cryptocurrency's market value crosses a price threshold. Cryptocurrency investors can sit back, let the market do its thing, and wait for opportunities instead of compulsively checking the markets!

Following Along

For the purpose of this tutorial, I have set up a repository with the complete code hosted Github: You will be able to build everything you need by following the steps in this post, but if you want to see what the completed project looks like at any step, you can clone this repository with the following command on your command line interface/terminal:

For each step in this tutorial, you can checkout a branch that has the complete code. For example, running the command git checkout step-1-simple-express-appinside the root directory of the project will give you the exact code this tutorial instructs you to write. (Don't worry, I will give you the specific branch names at each step.) After checking out the branch, run npm installto download any NPM packages that you need for the tutorial step.

If you get stuck, you can run and refer to the branch code to see a working example.

NOTE: To run this Node.js app from the command line, use npm start to start the app and Ctrl C to kill it.

What You'll Need

Before we get started, you will need to have some tools and software installed on your computer.

Node.js – Install the LTS version for your operating system. In this tutorial, I used version 8.9.4

MongoDB – For my local development on Mac OS X, I used Homebrew for my local MongoDB instance. You can choose from a number of options and operating systems here. Install the latest stable version (3.6.4 at the time of writing this article).

Twilio AccountSign up for a Twilio account if you don't have one already. (It's free!)

• Postman – A tool for testing APIs. In this tutorial, we will be interacting quite a bit with our custom API, so it helps to be able to generate and modify HTTP requests on the fly.

• If you haven't yet, sign up for a free Twilio account. After you have an account, you will be able to create your first project. If you already have an account with Twilio, navigate your browser to and create a project




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