copyJSON() - An easy way to copy values while allowing circular references to be omitted.

copyJSON.js

/**
 * @template T
 * @param {T} value
 * @param {boolean} [omitCircularRefs=false]
 * @returns {T}
 */
function copyJSON(value, omitCircularRefs = false) {
  const ancestors = new WeakSet();
  
  function recurse(value) {
    if ('object' !== typeof value || value === null) return value;
    let returnValue = Array.isArray(value) ? [] : {};
    ancestors.add(value);
    for (const [k, v] of Object.entries(value)) {
      if (!ancestors.has(v)) {
        returnValue[k] = recurse(v);
      }
    }
    ancestors.delete(value);
    return returnValue;
  }

  return JSON.parse(JSON.stringify((omitCircularRefs ? recurse(value) : value) ?? null));
}