Imagine a directed acyclic graph of nodes that describes the user's intent to transform data in various ways.

Assume the following:

• We have three types of nodes

  • Data - a table data
  • Join - joins two tables of data using a merge strategy
  • Filter - given a table of data filters it and returns a result

• The user is only interested in the results of certain Interesting nodes in the graph.

• The user can edit, add or remove nodes as they build their process and want to be notified when the results of an Interesting node have changed.

Take the following graph as an example when the user is interested in Data2 and Filter2. We want the following

• When Data1 changes we want to execute the parts of the graph necessary to show the new data passed through Filter2.
• When Data2 changes we want to execute the parts of the graph necessary to show the new data passed through Data2 and Filter2
• We never want to execute more that the necessary number of steps to get the user new data

Write a function (and tests) that given a graph, the set of interesting nodes, and a set of changed nodes returns a new graph containing just the operations we need to execute to display the new data.

Given the above graph, with interest in node Filter2 and a change in Join return this graph [ 'Data1', 'Data2', 'Join', 'Filter2' ]

• Install node.js we love using nvm to mange node versions
• Install project dependencies npm install
• Run the unit tests to make sure it worked npm test

If you don't have a favorite editor I suggest webstorm setup as follows

• Install webstorm
• Open webstorm and file > open... this projects directory
• Setup es6 - file > settings > Languages and Frameworks > Javascript from the dropdown choose ECMAScript 6
• Setup linter - file > settings in the search bar type eslint in the menu that comes up check the enable box at the top

Install the project dependencies

npm install 

Lint the code and run the tests on the commandline

npm test // lint and run tests

Start a development server and run the tests in the browser (useful for debugging)

npm run test-web
open localhost:8080/test.bundle // the tests are now running here