30-seconds-of-code/snippets/deepClone.md

title, tags

title	tags
deepClone	object,recursion,intermediate

Creates a deep clone of an object. Clones primitives, arrays and objects, excluding class instances.

Use recursion. Check if the passed object is null and, if so, return null. Use Object.assign() and an empty object ({}) to create a shallow clone of the original. Use Object.keys() and Array.prototype.forEach() to determine which key-value pairs need to be deep cloned. If the object is an Array, set the clone's length to that of the original and use Array.from(clone) to create a clone.

const deepClone = obj => {
  if (obj === null) return null;
  let clone = Object.assign({}, obj);
  Object.keys(clone).forEach(
    key => (clone[key] = typeof obj[key] === 'object' ? deepClone(obj[key]) : obj[key])
  );
  if (Array.isArray(obj)) {
    clone.length = obj.length;
    return Array.from(clone);
  }
  return clone;
};

const a = { foo: 'bar', obj: { a: 1, b: 2 } };
const b = deepClone(a); // a !== b, a.obj !== b.obj