submit-social-housing-lettings-and-sales-data/app/frontend/controllers/numeric_question_controller.js

import { Controller } from '@hotwired/stimulus'

export default class extends Controller {
  connect () {
    const affectedField = this.element.dataset.target
    const targetQuestion = affectedField.split('lettings-log-')[1].split('-field')[0]
    const div = document.getElementById(targetQuestion + '_div')
    div.style.display = 'block'
  }

  calculateFields () {
    const affectedField = this.element.dataset.target
    const fieldsToAdd = JSON.parse(this.element.dataset.calculated).map(x => `lettings-log-${x.replaceAll('_', '-')}-field`)
    const valuesToAdd = fieldsToAdd.map(x => getFieldValue(x)).filter(x => x)
    const newValue = valuesToAdd.map(x => parseFloat(x)).reduce((a, b) => a + b, 0).toFixed(2)
    const elementToUpdate = document.getElementById(affectedField)
    elementToUpdate.value = newValue
  }
}
const getFieldValue = (field) => {
  const elementFieldToAdd = document.getElementById(field)
  if (elementFieldToAdd) {
    return elementFieldToAdd.value
  }
  return document.getElementById(`${field}-error`).value
}