jQuery's .load() in pure JavaScript - Version using fetch

loadContent.js

/**
 * Loads an HTML document from a URL (or a portion of it via the “selector” parameter) within a “target” element.
 * If present, executes upon completion, a callback.
 *
 * Example usage:
 * loadContent('#target', 'https://www.mypage.tld');
 * loadContent('#target', 'https://www.mypage.tld', '#selector');
 * loadContent('#target', 'https://www.mypage.tld', '#selector', () => console.log('Hi!'));
 * loadContent('#target', 'https://www.mypage.tld', '#selector', myCallback);
 * loadContent('#target', 'https://www.mypage.tld', '', myCallback);
 *
 * @method loadContent
 * @param {string} target
 * @param {string} url
 * @param {string} selector
 * @param {function} callback
 */

const checkURL = url => {
    try { 
        return Boolean(new URL(url)); 
    } catch(e) { 
        return false; 
    }
}

const isEmpty = (args) => (args === "" || args === 0 || args === "0" || args === null || args === !1 || args === undefined || args.length === 0);

const loadContent = async function(target, url, selector, callback) {
    if (typeof target === 'string' && !isEmpty(target)) {
        if (typeof url === 'string' && !isEmpty(url)) {
            if (checkURL(url)) {
                if (document.querySelectorAll(target).length > 0) {
                    const trg = document.querySelector(target);
                    trg.innerHTML = '';

                    try {
                        const response = await fetch(url);
                        if (!response.ok) {
                          throw new Error(`Response status: ${response.status}`);
                        }

						const dt = await response.text();

                        if (typeof selector === 'string' && !isEmpty(selector)) {
                          const parser = new DOMParser();
                          const htmlDoc = parser.parseFromString(dt, "text/html");

                          if (htmlDoc.querySelectorAll(selector).length > 0) {
                            const section = htmlDoc.querySelector(selector);
                            trg.appendChild(section);
                          } else {
                            throw new Error('Invalid selector: ', selector);
                          }
                        } else {
                          trg.innerHTML = dt;
                        }

                        if (typeof callback !== 'undefined' && typeof callback !== null) {
                          if (typeof callback === 'function') {
                            callback();
                          } else {
                            throw new Error('Invalid callback: ', callback);
                          }
                        }
                    } catch (error) {
                      console.error(error.message);
                    }
                } else {
                    throw new Error('Invalid target: ', target);
                }
            } else {
                throw new Error('Invalid URL: ', url);
            }
        } else {
            throw new Error('Invalid URL: ', url);
        }
    } else {
        throw new Error('Invalid target: ', target);
    }
}