An example of static, serialized logic for how an application model should be processed

serialized-model-logic.js

const endOfTime = '9999-12-31'

const conditions = [
  {
    demographic: {
      gender: 'female',
      dob: '1954-10-06',
    },

    retirement: {
      type: 'fixed',
      value: '2020-09-06',
    },
  },

  {
    demographic: {
      gender: 'female',
      dob: '1960-05-06',
    },

    retirement: {
      type: 'addition',
      value: {
        years: 66,
        months: 1,
      },
    },
  },

  {
    demographic: {
      gender: 'female',
      dob: endOfTime,
    },

    retirement: {
      type: 'addition',
      value: {
        years: 68,
      },
    },
  },
]

const $ = selector => 
  document.querySelector(selector)
  
const demographicMatch = ({subject, target}) =>
  subject.gender === target.gender
  && moment(subject.dob).isBefore(target.dob)

const calculate = () => {
  const dob = $('#dob').value
  const gender = $('#gender').value
 
  const match = conditions.find(condition => 
    demographicMatch({
      subject : {dob, gender},
      target : condition.demographic
    })
  )
  
  // This nested ternary queries the match 
  // and produces a string indicating our outcome
  // In a structured application you'd probably break out this function
  // so that it can be tested independently
  const outcome = (
    ! match ? 'No idea'
    : moment(
      match.retirement.type === 'addition'
      ? moment(dob).add(match.retirement.value)
      : moment(match.retirement.value)
    ).format('MMMM YYYY')
  )
  
  $('#pensionDate').innerHTML = outcome
}

document.addEventListener('input', calculate)

calculate()