copy.js

/*!
 * Create an immutable clone of data (an array, object, map, set, etc.)
 * (c) 2021 Chris Ferdinandi, MIT License, https://gomakethings.com
 * @param  {*} obj The data object to copy
 * @return {*}     The clone of the array or object
 */
function copy (obj) {

	//
	// Methods
	//

	/**
	 * Copy properties from the original object to the clone
	 * @param {Object|Function} clone The cloned object
	 */
	function copyProps (clone) {
		for (let key in obj) {
			if (Object.prototype.hasOwnProperty.call(obj, key)) {
				clone[key] = copy(obj[key]);
			}
		}
	}

	/**
	 * Create an immutable copy of an object
	 * @return {Object}
	 */
	function cloneObj () {
		let clone = {};
		copyProps(clone);
		return clone;
	}

	/**
	 * Create an immutable copy of an array
	 * @return {Array}
	 */
	function cloneArr () {
		return obj.map(function (item) {
			return copy(item);
		});
	}

	/**
	 * Create an immutable copy of a Map
	 * @return {Map}
	 */
	function cloneMap () {
		let clone = new Map();
		for (let [key, val] of obj) {
			clone.set(key, copy(val));
		}
		return clone;
	}

	/**
	 * Create an immutable clone of a Set
	 * @return {Set}
	 */
	function cloneSet () {
		let clone = new Set();
		for (let item of set) {
			clone.add(copy(item));
		}
		return clone;
	}

	/**
	 * Create an immutable copy of a function
	 * @return {Function}
	 */
	function cloneFunction () {
		let clone = obj.bind(this);
		copyProps(clone);
		return clone;
	}


	//
	// Inits
	//

	// Get object type
	let type = Object.prototype.toString.call(obj).slice(8, -1).toLowerCase();

	// Return a clone based on the object type
	if (type === 'object') return cloneObj();
	if (type === 'array') return cloneArr();
	if (type === 'map') return cloneMap();
	if (type === 'set') return cloneSet();
	if (type === 'function') return cloneFunction();
	return obj;

}