js-level-2-projects/01-parse-a-csv-file/README.md

Exercise 01: CSV is Easy...Right?

This is exercise 01 of JavaScript Level 2 in Learn JavaScript the Hard Way. It is meant to be done as a challenge with incorrect starting code that you are expected to fix and improve. I repeat, this code is incorrect on purpose so you can fix it and attempt to do better.

• step1.js -- Use two projects to get CSV samples and try to write a simple parser that can parse all of the samples.
• step2.js -- This is a starter in case you are stuck, but it still fails and would fail on many CSV files. CSV is more complex than its name lets on.
• step3.js -- Take your parser and use the deep-equal project to compare your results to the csv-spectrum project's tests.
• step4.js -- Let's up the game and make this a unit test with ava, except it doesn't work because of promises/async/await not working with callbacks and events.
• step5.js -- First solution to step4.js that uses Promise directly to wrap callbacks and events.
• step6.js -- Second solution that uses util.promisify to convert the spectrum callback to a Promise automatically.

If you attempt this challenge then point me at your solution at @lzsthw and I'll take a look.

Learning Objectives

You aren't really learning about CSVs, but actually learning about how to deal with old APIs that use callbacks when you need Promises. The csv-spectrum library uses an old style of operation that loads your data then calls a function for you to process the data. These days APIs need Promises, and use async/await to deal with the promises. Using what you learned from the previous module JavaScript Level 1 you learned quite a lot about async/await/Promise/callbacks so now you apply that knowledge to deal with csv-spectrum.

If You Get Stuck

Remember the programming process of:

1. Write comments in human language describing what the code should do.
2. Write pseudo-code (p-code) under those comments to bridge from human to code.
3. Slowly convert the p-code to JavaScript and run your script repeatedly while you do.

If you're stuck chances are you're not following this process. If you need a clue about how to handle the csv-spectrum API then jump to the step5.js file to see one way, and step6.js to see another. Try to figure it out for yourself, and if you want a clue, remember that the resolve parameter to a Promise can be called inside a callback.