index.js

'use strict';

/**
 * @typedef {{ [key: string]: any }} Extensions
 * @typedef {Error} Err
 * @property {string} message
 */

/**
 *
 * @param {Error} obj
 * @param {Extensions} props
 * @returns {Error & Extensions}
 */
function assign(obj, props) {
    for (const key in props) {
        Object.defineProperty(obj, key, {
            value: props[key],
            enumerable: true,
            configurable: true,
        });
    }

    return obj;
}

/**
 *
 * @param {any} err - An Error
 * @param {string|Extensions} code - A string code or props to set on the error
 * @param {Extensions} [props] - Props to set on the error
 * @returns {Error & Extensions}
 */
function createError(err, code, props) {
    if (!err || typeof err === 'string') {
        throw new TypeError('Please pass an Error to err-code');
    }

    if (!props) {
        props = {};
    }

    if (typeof code === 'object') {
        props = code;
        code = '';
    }

    if (code) {
        props.code = code;
    }

    try {
        return assign(err, props);
    } catch (_) {
        props.message = err.message;
        props.stack = err.stack;

        const ErrClass = function () {};

        ErrClass.prototype = Object.create(Object.getPrototypeOf(err));

        // @ts-ignore
        const output = assign(new ErrClass(), props);

        return output;
    }
}

module.exports = createError;