Teaching Guide

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#BridgePattern Part 02

We are pushing toward the midterm now. This is not the midterm, but the code you are building now will be part of the midterm.

You should begin by building on top of your previous assignment. To distinguish between the work you did on BridgePattern01 assignment and the work you do in this assignment, you should create a git tag:

That will tag your current version of BridgeReader as version 1. You and I can both go back to this version when we want.

You will again use three patterns in this assignment:

We also use require and jasmine to test everything.

Base your code on on two or more of the following programs:

Create a DataReader object that can:

Continue using the Factory and Bridge patterns as before. For now, you can mock up displaying the markdown files, or actually display them in pagedown, depending on your preference. For the midterm, you will need to display it in a markdown editor called pagedown.

This time, I want everything but Factory in a pattern of some kind. In Main.js, just read in Factory, and then use the Factory to "create" (or pass on) all the other objects. Everything is a pattern. We are working only with abstractions for our major classes.

##Clickable List

Read in a list of filenames stored in JSON format from a file called FileList.json. It should look something like this, but the details are up to you:

    "Foo.json": "/home/bcuser/files/Foo.json",
    "Bar.json": "/home/bcuser/files/Bar.json",
    "Goober.json": "/home/bcuser/files/Goober.json",
    "Baz.json": "/home/bcuser/files/Baz.json"

Or what have you. Display the items in an unordered list and/or a series of radiobuttons. See Presidents.json for additional information on how to handle the auto generation of radiobuttons.

If you want, you can gussy up an unordered list with a few lines of CSS:

li {
  background-color: #00BBFF;
  border: black solid 1px;
  margin: 3px;
  width: 250px;  

li:hover {
    background-color: #00FFBB;

The CSS shown above puts each item in a list in its own block, and it highlights each item in turn as the user moves the mouse over it.

When the user clicks on a particular file name, read it in and display its contents to the user. You can use the Presidents.json file from BridgeReader01 as the basis for your Foo.json and Bar.json files, but each file must have unique content.

You cam read FileList.json in directly, but for the other files, you must send the file name and path, have the server get it from request.query or request.body, then read it in with fs.readFile (asynch version) and send it back via response.send.

##Property Names

Just a reminder. There are no rules about the names for properties in JavaScript. Thus we can create properties shaped like this:

"Foo.json": "/home/bcuser/files/Foo.json",

Note, however, that you can't write this to access the value for the property shown above:


Think about it for a second, and you can see why. (The second period is going to cause problems!)

You can, however, do this:

myJsonObject['Foo.json']; // Yields home/bcuser/files/Foo.json

##User Choice

When the user clicks on an item in our unordered list, we want to send a request back to the server based on the selection the user made. In particular, they click on a file name, and then send a request back to the server for the contents of the file the user selected.

Ideally, it is safest to keep all the information about filepaths on the server side, and never send it to the client. However, at this stage, it is probably okay for us to cheat. Here is a hurried explanation of how to keep track of two bits of information in a single list item.

The file list that we read in has two bits of information per line:

"Foo.json": "/home/bcuser/files/Foo.json",

There is a file name: Foo.json. There is also the path to the file: /home/bcuser/files/Foo.json. Here is how to encode both pieces of information in a list item:

$.getJSON('/read', fileObject, function(fileList) {
    var serverData = fileList;
    for (var file in serverData) {
        $('#displayList').append('<li data=' + serverData[file] + '>' + file + '</li>');

Now the list items in your unordered list look like this:

<li data="/home/charlie/Documents/Data/Presidents01.json">President01.json</li>

When the user clicks on the items, you can retrieve the data like this:

function pickFile(event) {
    var fileName = event.target.innerHTML;  // Was innerText
    var filePathName = event.target.attributes.data.value;


##Handling User Input

It is perhaps saying a word about what to do when the user clicks on a listitem to make a file selection. The best example of what you want to do is in ClickEvents.

When you respond to a click on a listItem, you want to call $.getJSON.


... // Code omitted here

var listClick = function(event) { 
   // Your getJSON code here.

The user clicks on a listItem and invokes the click handler shown above. Use .getJSON to invoke a route on the server and to send a simple JavaScript object to the server specifying the user's choice. Assuming you saved the path to the file in an attribute called data, as recommended above, you can get the user's choice like this:

$('#debug01').html("You picked: " + event.target.innerHTML) // innerText
$('#debug02').html("Value: " + event.target.attributes.data.value);

The server gets the call and uses request.query to discover the file the user requested. Use fs.readFile to read the file from disk. Use response.send to send the contents of the file back to the client. There are many examples of how to do this sort of thing in JsObjects, including AsyncJsonReader.

Parse the content of the file sent from the server. It is sent as a parameter to your $.getJSON callback. The callback is an anonymous function passed as the second parameter to $.getJSON. Display the parsed content to the user

##Test and run

To start the app I should be able to run:

npm start

To start the tests, I should be able to run:

node TestRunner.js

You must have at least 25 tests, no matter how trivial. For instance write tests that prove you can:

  1. Use require to reach your ReaderFactory
  2. Use require to reach your BridgeFactory
  3. Use require to reach your BridgeReader
  4. Use require to reach your FancyBridgeReader
  5. Use require to reach your JsonReader
  6. Use require to reach your MarkdownReader
  7. Use require to reach your DefaultReader
  8. Create a ReaderFactory
  9. Create a BridgeFactory
  10. Create a BridgeReader
  11. Create a FancyBridgeReader
  12. Create a JsonReader
  13. create a MarkdownReader
  14. create a DefaultReader
  15. Use a factory to create a JsonReader and prove it is a JsonReader:
    1. expect(jsonReader instanceof JsonReader).toBe(true);
  16. Create a MarkdownReader with a factory and prove it is a MarkdownReader
  17. Prove the DefaultReader with a factory and prove it is a DefaultReader
  18. Use hasOwnProperty to prove a jsonReader has a readFile method
  19. Use hasOwnProperty to prove a markdownReader has a readFile method
  20. Use hasOwnProperty to prove a defaultReader has a readFile method

If you can, when you type grunt jshint, I want it to come back clean.


You can place a markdown file such as this one in your public directory. Call it MarkdownSample.md:

# Markdown Sample Header

This is a sample markdown file. You can make lists like this:

- One
- Two
- Three

## Details

Try pasting the contents of this file into this editor:

- [StackEditIO](https://stackedit.io/)

That's the editor found at **https://Stackedit.io**

Then use Jade to create a pre in which you can display it:


And display it like this:


$.load is a wrapper around $.Ajax for use when you just want to load a file from the file system.

We will get a real markdown editor and display tool going next week.

For a working example, see the NodesRoutes03 example.

##Turn it in

Place your work in a folder called Week05BridgeReader02 and check it in to your repository. Submit a link to your repository.