Observer Pattern Assessment

From here on out the solution requirements are not as easy to define as input/output as the scale in which they operate has increased. I will try my best to describe what I want, but if something is unclear please reach out to me.

Prerequisites

1. Download and run all the demo's and familiarize yourself with the observer pattern.
2. Read / Watch the supplementary content
3. Download the exercise files

Exercises

1. Synchronize the Stocks (Callbacks Review)

   

    

   Starting with the Stock Portfolio Simulator example:

   Edit index.html replacing the multiple calls to console.log() with a single call to console.table() As console.table requires a single tabular dataset, the data must be condensed into a single array. Use synchronization techniques covered in assignment one, to only print the table after all newday events have come in.

   What columns you choose to print out do not matter. In my example I choose the simplest choice of printing out the entire emitted object. Do not worry about the formatting of individual data types.

    

   Helper functions used in my solution. Your solution might find these useful:

   `console.clear()`, `process.stdout.cursorTo(0, 1)`
   

    

    

2. Quote of the Day

   

    

   Using DayEmitter create two files:

   1. modules/QuoteEmitter.js

      • The constructor accepts a DayEmitter object. It listens for a newday event and emits a qotd event that includes a random quote as it's second argument.
      • A list of quotes can be found in data/quotes.json

   2. index.js that will print a calendar on each newday event and a quote on each qotd event.

      Use console.clear() to clear the console between days.

      Ignore issues with long lines wrapping in the console.

       

3. Price Notifications

   

    

   Starting with the Stock Portfolio Simulator (with a smaller portfolio) create two files:

   1. modules/PriceEmitter.js

      • The constructor accepts a Stock (emitter) object, a target_price, and direction (above or below)

        data/stock-alerts.json contains price alert data, but ensure Stock emitters are created first.

      • PriceEmitter emits a price-alert when a certain price threshold is passed. The second argument on the emitter should be an object containing date, ticker, target_price, direction, and price.

   2. index.js will listens for price-alert events and prints out a message to console.

       

4. Bad Word Detection

   

    

   This question has you writing a program to keep track of how many bad words a user has used in a fictional chat application.

   Create two files:

   1. modules/BadWordEmitter.js

      • The constructor accepts an array of badwords and a readline interface rl

        It will listens to line events from rl. For each word found that has a match inside badwords, emit a signal badword. Each badword signal does not have any additional data. If a user types in multiple Bad Words, multiple signals should be emitted.

      • A list of Bad Words can be found in data/badwords.json

      • Matches should be case insensitive.

   2. index.js listens for badword events and will keep a counter on top of the program. The counter should appears after the user has said their first bad word.

    

5. Morse Decoder

   

    

   Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signals, dots (.) and dashes (-). We add a third signal break to denote the end of a character, which is traditionally done by having a short pause.

    

   1. Create a file index.js that decodes the secret message emitted by MorseEmitterEncypted.js

      • Listen for events .,-, and break emitted by MorseEmitter
      • When a . or - event is heard add the respective symbol to a variable morse_character
      • When a break event is heard convert morse_character into an ascii character and print it using process.stdout.write()
      • Repeat until there are no more signals being emitted.

       

      Hints:

      • data/morse-code.json contains a table to assist in converting from morse.
      • Ignore spaces, they won't appear in my tests.

    

    

   2. The previous step must be completed first

      Create a file modules/MorseEmitter.js that acts as a replacement for MorseEmitterEncrypted.js. Your version will be improved, because it won't have a built in delay unlike mine.

      • The constructor accepts a string message representing the text to encode.
      • The MorseEmitter class should have a start() method, that when called will convert message into Morse code and then emit a combination of three signals (., -, and break) representing message.
      • These signals can then be picked up by index.js which from the previous step should be able to decode the the Morse code.

      Hints:

      • data/morse-code.json contains a table to assist in converting to morse.

      • Remove any spaces from the input before the conversion process starts.

      • Test your code by changing index.js to point to modules/MorseEmitter instead