Error with circular references to JSON

error-to-json.js

/**
 * Converts an Error object into a plain object with all its properties.
 * It includes non-enumerable properties like "message", "name", and "stack".
 *
 * @param {Error} error - The Error object to convert.
 * @returns {Object} A plain object containing the properties of the Error.
 */
const convertErrorToPlainObject = (error) =>
  Object.fromEntries(
    Object.getOwnPropertyNames(error).map((propertyName) => [
      propertyName,
      error[propertyName],
    ])
  );

/**
 * Creates a replacer function for JSON.stringify to handle circular references.
 * If a circular reference is detected, the value is replaced with the string "[Circular]".
 *
 * @returns {(this: any, key: string, value: any) => any} A replacer function that can be used with JSON.stringify.
 */
const createCircularReferenceReplacer = () => {
  /**
   * Tracks already visited objects to detect cycles.
   * 
   * WeakSet is used to track already visited objects. WeakSet is preferred
   * because it doesn't prevent garbage collection (unlike Set) and is
   * specifically designed to hold objects only.
   */
  const seenObjects = new WeakSet();

  return (_key, value) => {
    if (typeof value === "object" && value !== null) {
      if (seenObjects.has(value)) {
        return "[Circular]"; // Replace circular references with this placeholder.
      }
      seenObjects.add(value); // Mark this object as seen.
    }
    return value;
  };
};

/**
 * Serializes an Error object to a JSON string.
 * It converts the Error into a plain object and ensures circular references are handled.
 *
 * @param {Error} error - The Error object to serialize.
 * @returns {string} A JSON string representing the Error object.
 */
const errorToJson = (error) => {
  const handleCircularReferences = createCircularReferenceReplacer();

  const errorAsPlainObject = convertErrorToPlainObject(error);
  return JSON.stringify(errorAsPlainObject, handleCircularReferences, 2);
};

example.js

const exampleError = new Error("Something bad happened");
exampleError.self = exampleError; // Simulate a circular reference
console.log(errorToJson(exampleError));

// Prints `{"stack":"Error: Something bad happened\n    at <anonymous>:1:22","message":"Something bad happened","self":{"self":"[Circular]"}}`