03: Asynchronous Callbacks

Submission Instructions

• Work in a fork of this repository
• Work in a branch on your fork
• Write all of your code in a directory named lab- + <your name> e.g. lab-susan
• Open a pull request to this repository
• Submit on canvas a question and observation, how long you spent, and a link to your pull request

Resources

• fs module docs

Configuration

Configure the root of your repository with the following files and directories. Thoughfully name and organize any aditional configuration or module files.

• README.md - contains documentation
• .gitignore - contains a robust .gitignore file
• .eslintrc - contains the course linter configuratoin
• .eslintignore - contains the course linter ignore configuration
• package.json - contains npm package config
  • create a lint script for running eslint
  • create a test script for running tests
• lib/ - contains module definitions
• data/ - contains the text files used by the program
• __test__/ - contains unit tests

Testing

File Reader Module Tests

• Use describe and it methods to define descriptive tests and increase readability
• Each it callback should aim to test a small, well defined, feature of a function
• Write tests to ensure that the reader function rejects errors with invalid file paths
• Write tests to ensure that the reader function correctly resolves mapped string data for an array of file paths

Feature Tasks

File Reader Module

In the lib/ directory, create a reader.js module that exports a single function. The reader module should take an array of three file paths and console.log the first 8 bytes (in hex) of each file. You will need to create these files yourself and be sure to make their content and length different. Regardless of file size, all three files should be read and logged in the order one.txt, two.txt, three.txt.

• The file reader module should have the function signature (paths, callback) => undefined
• On failure, the file reader module should invoke the callback with an error callback(error)
• On success, the file reader module should invoke the callback with null as the first parameter and the result as the second parameter - callback(null, result)

Documentation

In your README.md describe the exported values of the module you have defined. Your file reader function description should include it's airty (expected number of parameters), the expected data for each parameter (data-type and limitations), and it's behavior (for both valid and invalid use). Feel free to add any additional information to your README.md that seems relavent and useful.