function _applyFilter()

in index.js [771:820]
39 lines of code
8 McCabe index (conditional complexity)

function _applyFilter (matchingProposals) {
  // filter out proposals based on the grouping checkboxes
  var allStateCheckboxes = document.querySelector('nav').querySelectorAll('.filter-by-status input:checked')
  var selectedStates = [].map.call(allStateCheckboxes, function (checkbox) { return checkbox.value })

  var selectedStateNames = [].map.call(allStateCheckboxes, function (checkbox) { return checkbox.nextElementSibling.innerText.trim() })
  updateFilterDescription(selectedStateNames)

  if (selectedStates.length) {
    matchingProposals = matchingProposals
      .filter(function (proposal) {
        return selectedStates.some(function (state) {
          return proposal.status.state.toLowerCase().indexOf(state.split('-')[0]) >= 0
        })
      })

    // handle version-specific filtering options
    if (selectedStates.some(function (state) { return state.match(/swift/i) })) {
      matchingProposals = matchingProposals
        .filter(function (proposal) {
          return selectedStates.some(function (state) {
            if (!(proposal.status.state === '.implemented')) return true // only filter among Implemented (N.N.N)
            if (state === 'swift-swift-Next' && proposal.status.version === 'Next') return true // special case

            var version = state.split(/\D+/).filter(function (s) { return s.length }).join('.')

            if (!version.length) return false // it's not a state that represents a version number
            if (proposal.status.version === version) return true
            return false
          })
        })
    }
  }

  var filteredProposals = proposals.filter(function (proposal) {
    return matchingProposals.indexOf(proposal) === -1
  })

  matchingProposals.forEach(function (proposal) {
    var matchingElements = [].concat.apply([], document.querySelectorAll('.' + proposal.id))
    matchingElements.forEach(function (element) { element.classList.remove('hidden') })
  })

  filteredProposals.forEach(function (proposal) {
    var filteredElements = [].concat.apply([], document.querySelectorAll('.' + proposal.id))
    filteredElements.forEach(function (element) { element.classList.add('hidden') })
  })

  updateProposalsCount(matchingProposals.length)
}