clone.js

// adapted from https://stackoverflow.com/a/40294058

export default function cloneDeep (data, hash = new WeakMap()) {
  if (Object(data) !== data) return data
  if (hash.has(data)) return hash.get(data)

  const result = data instanceof Date
    ? new Date(data)
    : (data instanceof RegExp
      ? new RegExp(data.source, data.flags)
      : (data instanceof Set
        ? new Set()
        : (data instanceof Map
          ? new Map()
          : (typeof data.constructor !== 'function'
            ? Object.create(null)
            : (data.prototype !== void 0 && typeof data.prototype.constructor === 'function'
              ? data
              : new data.constructor()
            )
          )
        )
      )
    )

  if (typeof data.constructor === 'function' && typeof data.valueOf === 'function') {
    const val = data.valueOf()

    if (Object(val) !== val) {
      const result = new data.constructor(val)

      hash.set(data, result)

      return result
    }
  }

  hash.set(data, result)

  if (data instanceof Set) {
    data.forEach(val => {
      result.add(cloneDeep(val, hash))
    })
  }
  else if (data instanceof Map) {
    data.forEach((val, key) => {
      result.set(key, cloneDeep(val, hash))
    })
  }

  return Object.assign(
    result,
    ...Object.keys(data).map(key => ({ [key]: cloneDeep(data[key], hash) }))
  )
}