https://www.vsfac.com/js/core/element.js?v=7.265.42.2

1/*
2  defining the <load-file> Web Component,
3  yes! the documenation is longer than the code
4  License: https://unlicense.org/
5  
6  modified from original authors version.
7  because longer code is better when it handles actual errors.
8*/
9customElements.define("load-file", class extends HTMLElement {
10
11  // declare default connectedCallback as sync so await can be used
12  async connectedCallback(
13    // call connectedCallback with parameter to *replace* SVG (of <load-file> persists)
14    src = this.getAttribute("src"),
15    // attach a shadowRoot if none exists (prevents displaying error when moving Nodes)
16    // declare as parameter to save 4 Bytes: 'let '
17    shadowRoot = this.shadowRoot || this.attachShadow({mode:"open"})
18  ) {
19      const response = await fetch(src);
20      if (response.ok)
21      {
22        // load SVG file from src="" async, parse to text, add to shadowRoot.innerHTML
23        shadowRoot.innerHTML = await (response).text()
24
25        // append optional <tag [shadowRoot]> Elements from <load-svg> innerHTML/lightDOM after parsed <svg>
26        shadowRoot.append(...this.querySelectorAll("[shadowRoot]"))
27
28        // if "replaceWith" attribute exists
29        // then replace <load-svg> with loaded content <load-svg>
30        // childNodes instead of children to include #textNodes also
31        this.hasAttribute("replaceWith") && this.replaceWith(...shadowRoot.childNodes);
32      }
33  }
34})