Master everything you need to know about Docker containers to easily create, deploy, and run your applications with containers.

DevOps for Developers

By now, you've probably heard the buzz around Docker. It's fundamentally changed the development process and been adopted by software teams of all sizes, and for good reason: Docker makes it considerably easier to create, deploy, and run applications with the use of containers.

Docker is here to stay, and is becoming one of the most in-demand technologies on the market. Mastering it now will help you produce better software, level up your career, and stand out from the crowd. Get started today.

Docker for Developers

In the [*create-docker-images/exercises/jsparam/starter*](https://bitbucket.org/epobb/dockerbookfiles/src/master/create-docker-images/exercises/jsparam/starter/compute.js) folder you'll find a *compute.js* file with the following code:


var radius = process.env.diameter / 2;
var area = Math.pow(radius, 2) * Math.PI;
console.log(
    `Area of a ${radius} cm radius disk:
    ${area} cm²`
);

It's a modified version of the code from the previous exercises. It expects a *`diameter`* environment variable to be available and displays the area of a disk for that given diameter. Create a Docker image that runs the code in `compute.js` file using the *node:11-alpine* image that contains Node.JS. Run two containers with different values for the diameter.


Test yourself and implement what you have learned so far in this exercise.

Exercise: Enable an Image to Be Parameterized