Frog.js

class Frog {
  constructor(name, gender, eyes, legs, scent, tongue, heart, weight, height) {
    if (!Array.isArray(legs)) {
      throw new Error('Parameter "legs" is not an array')
    }
    // Ensure that the first character is always capitalized
    this.name = name.charAt(0).toUpperCase() + name.slice(1)
    this.gender = gender
    // We are allowing the caller to pass in an array where the first index is the left eye and the 2nd is the right
    //    This is for convenience to make it easier for them.
    //    Or they can just pass in the eyes using the correct format if they want to
    //    We must transform it into the object format if they chose the array approach
    //      because some internal API uses this format
    this.eyes = Array.isArray(eyes) ? { left: eye[0], right: eye[1] } : eyes
    this.legs = legs
    this.scent = scent
    // Pretending some internal API changed the field name of the frog's tongue from "tongueWidth" to "width"
    //    Check for old implementation and migrate them to the new field name
    const isOld = 'tongueWidth' in tongue
    if (isOld) {
      const newTongue = { ...tongue }
      delete newTongue['tongueWidth']
      newTongue.width = tongue.width
      this.tongue = newTongue
    } else {
      this.tongue = newTongue
    }
    this.heart = heart
    if (typeof weight !== 'undefined') {
      this.weight = weight
    }
    if (typeof height !== 'undefined') {
      this.height = height
    }
  }
}

const larry = new Frog(
  'larry',
  'male',
  [{ volume: 1.1 }, { volume: 1.12 }],
  [{ size: 'small' }, { size: 'small' }, { size: 'small' }, { size: 'small' }],
  'sweaty socks',
  { tongueWidth: 18, color: 'dark red', type: 'round' },
  { rate: 22 },
  6,
  3.5,
)