Async load external CSS using JS

loadExternalCSS.js

export default function loadCSS(href: string, cb: Function | null) {
  if(!isStyleLoaded(href)) {
    const l: HTMLElement | null = document.createElement('link')
    l.setAttribute('rel', 'stylesheet')
    l.setAttribute('href', href)
    if(cb)
      l.onload = cb() 
    document.body.appendChild(l)
  }
}

//check is style loaded
function isStyleLoaded(href: string) {
  const styles: any = document.querySelectorAll('link[rel=\'stylesheet\']')
  // is css loaded
  for (let i = styles.length; i--;) {
    if(styles[i].href == href) return true
  }
}