deepClone.js

/**
 * Deep clones an object or array
 * @param {object|array} obj Object or array to clone
 * @returns {object|array} Cloned object or array
 */
function deepClone (obj) {
  if (typeof obj !== 'object' || obj === null) return {};

  const res = Array.isArray(obj) ? [] : {};
  const queue = [{ base: res, current: obj }];

  while (queue.length) {
    const { base, current } = queue.shift();
    const baseIsArray = Array.isArray(base);

    for (const [key, value] of Object.entries(current)) {
      const valueIsArray = Array.isArray(value);
      const valueIsObject = typeof value === 'object' && value !== null;

      if (baseIsArray) {
        if (valueIsArray) {
          const newBase = [];
          base.push(newBase);
          queue.push({ base: newBase, current: value });
        } else if (valueIsObject) {
          const newBase = {};
          base.push(newBase);
          queue.push({ base: newBase, current: value });
        } else {
          base.push(value);
        }
      } else {
        if (valueIsArray) {
          const newBase = base[key] = [];
          queue.push({ base: newBase, current: value });
        } else if (valueIsObject) {
          const newBase = base[key] = {};
          queue.push({ base: newBase, current: value });
        } else {
          base[key] = value;
        }
      }
    }
  }

  return res;
}