/backend-13-simpledb

Primary LanguageJavaScript

Simple Db

Demo

Use the copy file/dir demo to guide you in how to construct async workflows

Getting Started

Use this template to get started.

Don't forget to npm i!

Here is a link to the node fs docs

Learning Objectives

  • Sequential and parallel asynchronous workflows
  • Promise chaining
  • async/await syntax
  • Handling specific errors in async actions
  • Using a class to hold onto shared state and expose methods

Description

Write a JavaScript class that manages saving objects as json. A really simple, single-table database! It will used an id generation library from npm like shortid and store files in the format [id].json, like er3i5c.json. The contents of the file should be a JSON representation of the object using JSON.stringify.

Use can use async/await in your tests, but use promise chaining in your SimpleDb implementation.

Create a branch that you can submit as a PR!

It features the following methods:

constructor(directoryPath)

The class constructor should take the directory to use as a string and store it on the object instance. You do not need to explicitly test the constructor as it will be used in each test.

class SimpleDb {
    constructor(dirPath) {
        this.dirPath = dirPath;
    }
}

get(id)

Returns an object deserialized (JSON.parse) from the contents of the file with that id in the directory (don't forget to add .json!).

It will be helpful to write a test that constructs an artificial file in your directory (see the copyFile demo example), with an id and contents you control.

  • You can make up any id, and just make sure your contents string is valid JSON.
  • Your test should use .toEqual with an example JS object equivalent to the string you saved

get(id) not found

Write a test of get that checks for ENOENT in the implementation, bit converts it to a Not found error (see the copy file demo).

save(obj)

Takes an object, assigns a random id (sets an id property) and the serializes (JSON.stringify) the object into a file of name [id].json.

The object will be mutated after the method completes, so you can check the object after you call save in your test for the new id. Use the get(id) method as your test to see that the object was correctly saved. You can compare the object that you passed to save to the one returned from get(id) via .toEqual assertion.

getAll()

Get all the objects in the directory. This will require Promise.all and should use your existing get(id) method to get the object(s) (see copy dir demo).

Your test should start by saving a few objects to the store, then calling getAll and verify via .toEqual assertion.

Refactor to async/await

Open a PR from your initial dev branch to main

Stretch Goals

You can do the stretch goals directly using async/await (unless you really want to practice more promise chaining syntax, in which case make sure to covert once you have tests working!)

Refactor file path method

Your SimpleDb class likely has repeated code for create the file path from the id. Create a private method #getFilePath that the other methods use to do this work.

delete(id)

Remove a stored object by id. Add a second test that if given a id that doesn't exists, it does not throw an error (because it already is "deleted")

Acceptance Criteria

You should have 2 branches with 2 PRs:

  • dev to main with Promise chaining implementation
  • async-await to dev with refactor to async/await

Both PRs should have passing CI

Rubric

Each method needs to be fully tested

Task Points
save(obj) 5
get(id) 5
getAll() 5
refactor to async/await 5