function encode(str) {
  return encodeURIComponent(str).replace("-", "%2D")
}

let sel = window.document.getSelection(),
    ctx = sel?.anchorNode?.parentElement?.textContent?.split(sel),
    anc = sel.toString() ? `:~:text=${ctx[0] ? encode(ctx[0])+"-," : ""}${sel}${ctx[1] ? ",-"+encode(ctx[1]) : ""}` : ""

let url = new URL(window.location)
if (anc) url.hash = anc
url.toString()