import { IS_BROWSER } from '../../constants'; /** * Adds an `@import` stylesheet reference to the * if it does not already exist. */ export function importStylesheet(url: string) { if (!IS_BROWSER) { return; } if (exists('style', url)) { return; // NB: Only add to the document once. } // const head = document.head || document.getElementsByTagName('head')[0]; const head = document.head; const style = document.createElement('style'); style.type = 'text/css'; const css = `@import url('${url}')`; style.dataset.url = url; style.appendChild(document.createTextNode(css)); head.appendChild(style); } /** * INTERNAL */ function exists(tag: 'style', url: string) { return IS_BROWSER ? Boolean(findByUrl(tag, url)) : false; } function findByUrl(tag: 'style', url: string) { if (IS_BROWSER) { const items = Array.from(document.getElementsByTagName(tag)); return items.find(style => style.dataset.url === url); } else { return undefined; } }