js: target very first latter of words

select.html

window.onload = function(){
  var elements = document.getElementsByClassName("each-word")
  for (var i=0; i<elements.length; i++){
    elements[i].innerHTML = elements[i].innerHTML.replace(/\b([a-z])([a-z]+)?\b/gim, "<span class='first-letter'>$1</span>$2")
  }
}


<style>
  .first-letter {
    color: red;
  }
</style>
<p class="each-word">First letter of every word is now red!</p>