Deep Clone for TS

deepClone.ts

function isObject(obj: unknown): obj is Record<string, unknown> {
  return typeof obj === 'object' && obj !== null
}

export function deepClone<T>(obj: T, cache: Map<unknown, unknown> = new Map()): T {
  if (obj === null || typeof obj !== 'object') {
    return obj
  }

  if (cache.has(obj)) {
    return cache.get(obj) as T
  }

  let result: unknown

  if (obj instanceof Date) {
    result = new Date(obj.getTime())
  } else if (obj instanceof Buffer) {
    result = Buffer.from(obj)
  } else if (ArrayBuffer.isView(obj) && obj.buffer instanceof ArrayBuffer) {
    result = (obj as unknown as ArrayBuffer).slice(0)
  } else if (obj instanceof Map) {
    const resultMap = new Map()
    cache.set(obj, resultMap)
    for (const [key, value] of obj.entries()) {
      resultMap.set(deepClone(key, cache), deepClone(value, cache))
    }
    result = resultMap
  } else if (obj instanceof Set) {
    const resultSet = new Set()
    cache.set(obj, resultSet)
    for (const value of obj.values()) {
      resultSet.add(deepClone(value, cache))
    }
    result = resultSet
  } else if (typeof obj === 'function') {
    result = obj
  } else if (isObject(obj)) {
    const newObj: Record<string, unknown> = {}
    cache.set(obj, newObj)
    Object.keys(obj).forEach(key => {
      newObj[key] = deepClone(obj[key], cache)
    })
    result = newObj
  } else {
    result = obj
  }

  return result as T
}