Rudimentary JavaScript object deep copy.

README.md

Rudimentary JavaScript object deep copy

Function to perform a deep copy of an object - rudimentary in that it will only handle the following types:

• Primitives
• Array
• Object

Basically can perform the following, but also copy undefined:

const clone = JSON.parse(JSON.stringify(myObj));

Also will handle circular references from the item source, such as:

const source = {
	one: 1,
	two: 2,
};

source.three = source;
const clone = copy(source);

copy.js

'use strict';

function copy(item,seen = new WeakMap()) {
	// primitive type?
	if (!(item instanceof Object)) {
		return item;
	}

	// property already cloned?
	if (seen.get(item)) {
		// return prior clone - avoid circular references
		return seen.get(item);
	}

	if (Array.isArray(item)) {
		// array type
		const clone = [];
		seen.set(item,clone);
		for (const value of item) {
			clone.push(copy(value,seen));
		}

		return clone;
	}

	// `{}` type
	const clone = {};
	seen.set(item,clone);
	for (const key of Object.keys(item)) {
		clone[key] = copy(item[key],seen);
	}

	return clone;
}