FrogBuilder.js

class FrogBuilder {
  constructor(name, gender) {
    // Ensure that the first character is always capitalized
    this.name = name.charAt(0).toUpperCase() + name.slice(1)
    this.gender = gender
  }
  formatEyesCorrectly(eyes) {
    return Array.isArray(eyes) ? { left: eye[0], right: eye[1] } : eyes
  }
  setEyes(eyes) {
    this.eyes = this.formatEyes(eyes)
    return this
  }
  setLegs(legs) {
    if (!Array.isArray(legs)) {
      throw new Error('"legs" is not an array')
    }
    this.legs = legs
    return this
  }
  setScent(scent) {
    this.scent = scent
    return this
  }
  updateTongueWidthFieldName(tongue) {
    const newTongue = { ...tongue }
    delete newTongue['tongueWidth']
    newTongue.width = tongue.width
    return newTongue
  }
  setTongue(tongue) {
    const isOld = 'tongueWidth' in tongue
    this.tongue = isOld
      ? this.updateTongueWidthFieldName(tongue, tongue.tongueWidth)
      : tongue
    return this
  }
  setHeart(heart) {
    this.heart = heart
    return this
  }
  setWeight(weight) {
    if (typeof weight !== 'undefined') {
      this.weight = weight
    }
    return this
  }
  setHeight(height) {
    if (typeof height !== 'undefined') {
      this.height = height
    }
    return this
  }
  build() {
    return new Frog(
      this.name,
      this.gender,
      this.eyes,
      this.legs,
      this.scent,
      this.tongue,
      this.heart,
      this.weight,
      this.height,
    )
  }
}

const larry = new FrogBuilder('larry', 'male')
  .setEyes([{ volume: 1.1 }, { volume: 1.12 }])
  .setScent('sweaty socks')
  .setHeart({ rate: 22 })
  .setWeight(6)
  .setHeight(3.5)
  .setLegs([
    { size: 'small' },
    { size: 'small' },
    { size: 'small' },
    { size: 'small' },
  ])
  .setTongue({ tongueWidth: 18, color: 'dark red', type: 'round' })
  .build()

solution to code clutter for complex objects like - https://gist.github.com/jsmanifest/8e150cfd40fcbf23f822e7a2e5efaf8c#file-frog-js