function addEventListeners()

in index.js [530:606]
58 lines of code
11 McCabe index (conditional complexity)

function addEventListeners () {
  var nav = document.querySelector('nav')

  // typing in the search field causes the filter to be reapplied.  
  nav.addEventListener('keyup', filterProposals)
  nav.addEventListener('change', filterProposals)

  // clearing the search field also hides the X symbol
  nav.querySelector('#clear-button').addEventListener('click', function () {
    nav.querySelector('#search-filter').value = ''
    nav.querySelector('#clear-button').classList.toggle('hidden')
    filterProposals()
  })

  // each of the individual statuses needs to trigger filtering as well
  ;[].forEach.call(nav.querySelectorAll('.filter-by-status input'), function (element) {
    element.addEventListener('change', filterProposals)
  })

  var expandableArea = document.querySelector('.filter-options')
  var implementedToggle = document.querySelector('#filter-by-implemented')
  implementedToggle.addEventListener('change', function () {
    // hide or show the row of version options depending on the status of the 'Implemented' option
    ;['#version-options', '#version-options-label'].forEach(function (selector) {
      expandableArea.querySelector(selector).classList.toggle('hidden')
    })

    // don't persist any version selections when the row is hidden
    ;[].concat.apply([], expandableArea.querySelectorAll('.filter-by-swift-version')).forEach(function (versionCheckbox) {
      versionCheckbox.checked = false
    })
  })

  document.querySelector('.filter-button').addEventListener('click', toggleFiltering)

  var filterToggle = document.querySelector('.filter-toggle')
  filterToggle.querySelector('.toggle-filter-panel').addEventListener('click', toggleFilterPanel)

  // Behavior conditional on certain browser features
  var CSS = window.CSS
  if (CSS) {
    // emulate position: sticky when it isn't available.
    if (!(CSS.supports('position', 'sticky') || CSS.supports('position', '-webkit-sticky'))) {
      window.addEventListener('scroll', function () {
        var breakpoint = document.querySelector('header').getBoundingClientRect().bottom
        var nav = document.querySelector('nav')
        var position = window.getComputedStyle(nav).position
        var shadowNav // maintain the main content height when the main 'nav' is removed from the flow

        // this is measuring whether or not the header has scrolled offscreen
        if (breakpoint <= 0) {
          if (position !== 'fixed') {
            shadowNav = nav.cloneNode(true)
            shadowNav.classList.add('clone')
            shadowNav.style.visibility = 'hidden'
            nav.parentNode.insertBefore(shadowNav, document.querySelector('main'))
            nav.style.position = 'fixed'
          }
        } else if (position === 'fixed') {
          nav.style.position = 'static'
          shadowNav = document.querySelector('nav.clone')
          if (shadowNav) shadowNav.parentNode.removeChild(shadowNav)
        }
      })
    }
  }

  // on smaller screens, hide the filter panel when scrolling
  if (window.matchMedia('(max-width: 414px)').matches) {
    window.addEventListener('scroll', function () {
      var breakpoint = document.querySelector('header').getBoundingClientRect().bottom
      if (breakpoint <= 0 && document.querySelector('.expandable').classList.contains('expanded')) {
        toggleFilterPanel()
      }
    })
  }
}