Description
This assignment will help you learn and practice JavaScript syntax, and use built-in and
user-defined functions.
Please do this assignment on your own. You should not work in partners, and all code must
be written by you. Gaining experience with JavaScript and the web takes a lot of personal
practice, and working on these problems yourself will help build your skill.
Submission
To hand in your work, see the “Submitting your Assignment” section below.
Please read and follow all instructions below carefully. If you have problems or questions,
talk to your professor.
Setup
This assignment uses a technique called “Unit Testing”, and relies on a number of
dependencies, which must be installed on your computer. A dependency is a library, tool,
or other piece of software that is needed in order to build, test, and run another piece of
software. JavaScript projects often rely on hundreds or thousands of dependencies, and
getting used to installing and using them is an important step.
In order to install these dependencies, you must first install Node.js on your computer. See
installation instructions at:
https://nodejs.org/en/
You can install the LTS (Long Term Support) version of node.js, which is currently 12.18.3,
although any 12.x.x version should work.
Install Dependencies
Open a command line terminal (e.g., cmd.exe) and navigate (i.e., cd) to the directory where
you have unzipped the assignment files. When you type dir (Windows) or ls
(Linux/macOS) you should see this README.md file, package.json, etc.
In this directory, install the assignment dependencies using the Node.js Package Manager
command, named npm. The npm command is installed along with node.js. In your terminal,
type the following:
npm install
This will download and save all the necessary dependency files to a folder named
node_modules/ in the current directory. You should see a node_modules folder next to
your package.json.
If you have trouble getting “npm install” to work:
• Did you install node.js?
• If you type “node –version” in your terminal, does it print the version?
• Are you in the right directory (you must cd into the correct directory)
If you need help, ask your classmates and/or talk to your professor.
Install a Proper Editor
You will need a proper editor to write code for the web. The most popular choice is
Microsoft Visual Studio Code (aka, VSCode). VSCode runs on Windows, Linux, and macOS.
You can download and install it for free from:
https://code.visualstudio.com/
NOTE: VSCode is not the same as Visual Studio. You should have both installed
A number of extensions are available that will work automatically with the scripts and
configuration in this project, and are recommended:
• eslint https://marketplace.visualstudio.com/items?itemName=dbaeumer.vscodeeslint
• prettier https://marketplace.visualstudio.com/items?itemName=esbenp.prettiervscode
When you open this project’s folder, VSCode should offer to install these recommended
extensions. Once these are installed VSCode will automatically show you errors as you
type, automatically format your code when you save, and show you spelling mistakes in
your code comments and names.
If you want to use a different editor, that’s fine. Confirm with your professor that it will
work for our needs. You may not use Notepad, for example.
Learn how to Navigate the Code
The assignment has a mix of project configuration and source code. All of the config files
are in the project root, and the source code is contained in the src directory (this is a
common pattern). Your code goes in the src/solution.js file. The other files in this
directory are unit tests, which you should read, but don’t need to modify.
Learn how to Run the Assignment Tests
You are asked to complete the code in the file src/solutions.js. A basic file layout has
already been created with various functions and variables. Also, detailed comments have
been left above each function you need to implement.
In addition, unit tests have been written for each function. They are named src/problem0.test.js, src/problem-1.test.js and so on. A Unit Test tests the smallest possible unit
of a software system or component, and we write many small Unit Tests to prove that our
implementation works as we expect.
For example, we expect 2 + 2 to return 4, not 5. We can write a unit test for this to confirm
that our code does what we expect. See http://softwaretestingfundamentals.com/unittesting/ for more info about unit tests.
These tests will help you determine if your code is working correctly: running the tests
should produce the output that the tests expect, and that tests will either pass or fail.
To run the tests, use the npm command:
npm test
Your goal is to get all of the tests to pass correctly. If a test fails, pay attention to the error
messages that get produced, what was expected vs. what was actually returned, and make
corrections to your code in assignment1.js.
Differnet Ways to Run Tests
If you are going to run your tests over and over as you make changes to src/solutions.js,
you can run the tests so they automatically watch for changes, and re-run whenever you
save your file:
npm run test-watch
You can stop the tests from running using CTRL + c.
Next, you can run a single test instead of all tests:
npm test problem-0
This will only run the tests in problem-0.test.js, making it easier to work on only one
problem at a time.
You can also watch a particular test, and re-run it when the code is saved:
npm run test-watch problem-0
Learn how to Lint your Code
In addition to running unit tests, you can also run a linter called eslint. Linting helps to
find and remove common errors in code, for example, missing a semi-colon, or forgetting to
declare a variable.
To run eslint, use the npm command:
npm run eslint
If there are no problems, there will be no output. If there is any output, pay attention to
what it says, so you can make corrections. For example:
assignment1/assignment1.js
18:9 error ‘x’ is defined but never used no-unused-vars
Here, we see a lint error, which has various information:
1. The filename is listed first, assignment1/assignment1.js
2. The line number is listed next: 18
3. The column number on line 18 is listed next: 9
4. The actual error or warning comes next: error ‘x’ is defined but never used
5. The rule name comes last: no-unused-vars. You can lookup how to fix these errors
using the rule name, for example: https://eslint.org/docs/rules/no-unused-vars
Your code should have no lint errors when you submit it.
Learn how to Properly Format your Code
Source code needs to be properly structured, use consistent indenting, semi-colons, etc.
Doing so makes it easier to understand, read, and debug your code.
Your code must be properly and consistently formatted. You can do it by hand, or, you can
use Prettier (https://prettier.io/) to do it automatically.
There are two ways to use Prettier. First, using the npm command:
npm run prettier
This will rewrite your files to use proper formatting. NOTE: running this command will
overwrite your file, so make sure you have saved your work before you run it.
The second way to run Prettier is using the Prettier extension, and format-on-save. If you
install the recommended extensions and settings for this project, saving your file will result
in Prettier automatically fixing your code for you.
Debugging Code and Tests
You can also use VSCode’s built in debugging tools to run and debug your code,
or the test code, within the editor, step through code, inspect variables,
examine call stacks, etc. See the instructions at: https://github.com/microsoft/vscoderecipes/tree/master/debugging-jest-tests#debugging-all-tests
Submitting your Assignment
When you have completed your assignment, you need to prepare your submission. To do
so, use the npm command:
npm run prepare-submission
This will do a number of things automatically for you:
• create a submission/ directory, deleting an existing one if present
• run prettier on the source
• copy all files under src/ to submission/src
• copy package.json to submission/package.json
• run eslint and write the output to submission/eslint.log
• run npm test and write the output to submission/test.log
• zip the submission/* directory to submission.zip
You can upload submission.zip to Blackboard for submission.
Discussion of Other Assignment Files
You may be wondering about some of the other files in this project. While you don’t need to
modify them, or use them directly, here is what each one does:
node_modules/ – the installed dependencies necessary to run prettier, eslint, etc., installed
when your run npm install.
.eslintrc.js – configuration for eslint, see https://eslint.org/docs/user-guide/configuring
.prettierrc.js – configuration settings for prettier, see
https://prettier.io/docs/en/configuration.html
package.json – node.js package info, dependencies, build scripts, see
https://docs.npmjs.com/files/package.json
package-lock.json – a generated file with dependency version information, see
https://docs.npmjs.com/files/package-lock.json
