deepCopy.js

const copy = item => {
	return !item ? item
			: Array.isArray(item) ? deepArrayCopy(item)
			: Object.prototype.toString.call(item).includes('Date') ? new Date(item.getTime())
			: typeof item === 'object' ? deepCopy(item)
			: item
}

const deepCopy = obj => {
	const objKeys = Object.keys(obj)
	const newObj = {}

	let i = objKeys.length
	let key
	while(i--) {
		key = objKeys[i]
		item = obj[key]
		newObj[key] = copy(item)
	}
	return newObj
}

const deepArrayCopy = arr => {
	let i = arr.length
	let item
	const newArr = []
	while(i--) {
		item = arr[i]
		newArr[i] = copy(item)
	}
	return newArr
}