JavaScript Programming Exercise

filter.js

// Railslove JavaScript programming exercise A1
//
// To run the following exercise you need to have mocha installed.
// Install mocha with yarn global add mocha or npm install -g mocha
//
// Then watch the output of `mocha filter.js` and see 4 of 5 failing tests.
//
// The task is to filter a given collection (L#35) for entries that contain unique pairs.
// While filtering return the same structure and keep the ranking.
// Write code in the body of the filter method to make the tests pass.
// Refactor until you're happy with your solution, by asking the follwing questions:
//   * Is the code understandable/maintainable?
//   * Do I really need all these if/else/elsif statements?
//
// In case you're wondering where all the semicolons are, this exercise is written
// in JavaScript Standard Style: https://standardjs.com

const assert = require('assert')

let filter = (collection, a = null, b = null) => {
  // Your code goes here  
  return collection
}

// don't touch me
let all = [
  { '1': ['A', 'B'] },
  { '2': ['A', 'C'] },
  { '3': ['D', 'E'] },
  { '4': ['F', 'G'] },
  { '5': ['E', 'A'] },
  { '6': ['C', 'H'] },
  { '7': ['D', 'B'] }
]

filter(all, 'A')

describe('#filter', () => {
  it('does not filter with empty params', () => {
    assert.deepEqual(filter(all), all)
  })

  it('filters one result', () => {
    assert.deepEqual(filter(all, 'H'), [{'6': ['C', 'H']}])
  })

  it('filters many results', () => {
    assert.deepEqual(filter(all, 'A'), [{'1': ['A', 'B']}, {'2': ['A', 'C']}, {'5': ['E', 'A']}])
  })

  it('filters with 2 parameters', () => {
    assert.deepEqual(filter(all, 'A', 'C'), [{'2': ['A', 'C']}])
  })

  it('filters order independent', () => {
    assert.deepEqual(filter(all, 'C', 'A'), [{'2': ['A', 'C']}])
  })
})