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Normalize URLs

Test-driven development is a popular method of writing software. The idea is that you write tests for your code first, then you write the code that gets the tests to pass. We're going to approach this project using a bit of TDD.

Normalizing URLs

We need a function that accepts a URL string as input and returns a "normalized" URL. To "normalize" means to "make the same". For example, all of these URLs are the "same page" according to most websites and HTTP standards:

https://www.boot.dev/blog/path/
https://www.boot.dev/blog/path
http://www.boot.dev/blog/path/
http://www.boot.dev/blog/path

We want our normalizeURL() function to map all of those same inputs to a single normalized output: www.boot.dev/blog/path.

Keep in mind, the normalized URL isn't going to be used to make requests, it's just going to be used to compare URLs to see if they are the same page.

Stub the Function

In test driven development (TDD), you typically follow this flow:

Stub out the function
Write the tests
Write the code that passes the tests

You are going to be using the Vitest testing library for TypeScript.

Assignment

Install vitest in your project as a dev dependency using npm:

npm install -D vitest

Add a test script property to your package.json file:

...
"scripts": {
  "start": "tsx ./src/index.ts",
  "test": "vitest run"
},
...

In our src directory, create a file called crawl.ts and create a function called normalizeURL. Make sure to export it from the module (file).

I'd recommend you read up on Vitest's getting started guide here. By default, the vitest command will look for files that end in .test.ts, so write your first tests in a file called crawl.test.ts in the src directory.

Write a few tests! Remember, this function should take a single URL (string) and return the normalized version of the URL as a string. This will help us later to detect whether two different URLs are the same web page, which is all our users care about. Try to test all the edge-cases you can think of.
Run your tests with npm run test. This works because you added the "test" script to package.json. You should see some failing tests now, which is expected because you haven't filled in the normalizeURL function yet.
Write the normalizeURL Function. I recommend using the URL object from the Node API. It parses a URL string into a URL object with some properties that will be useful to you.

Run and submit the CLI tests from the root of the module.