tiptap/packages/tiptap-core/src/utils/injectCSS.ts

export default function (css: string) {
  if (process.env.NODE_ENV !== 'test') {
    const style = document.createElement('style')
    style.type = 'text/css'
    style.textContent = css
    const { head } = document
    const { firstChild } = head

    if (firstChild) {
      head.insertBefore(style, firstChild)
    } else {
      head.appendChild(style)
    }
  }
}