Regex che trova la parola nella pagina

Questo codice mi trova la stessa parola nella pagina, ma solo qualcuna, es. se nella pagina ho 10 parole “casa” me ne trova solo qualcuna, non tutte 10.

<script>
jQuery.fn.highlight = function(what, spanClass) {
  return this.each(function() {
    var container = this,
      content = container.innerHTML,
      pattern = new RegExp('(>[^<.]*)(' + what + ')([^<.]*)', 'ig'),
      replaceWith = '$1<span ' + (spanClass ? 'class="' + spanClass + '"' : '') + '">$2</span>$3',
      highlighted = content.replace(pattern, replaceWith);
    container.innerHTML = highlighted;
  });
}

var getUrlParameter = function getUrlParameter(sParam) {
  var sPageURL = decodeURIComponent(window.location.search.substring(1)),
    sURLVariables = sPageURL.split('&'),
    sParameterName,
    i;

  for (i = 0; i < sURLVariables.length; i++) {
    sParameterName = sURLVariables[i].split('=');

    if (sParameterName[0] === sParam) {
      return sParameterName[1] === undefined ? true : sParameterName[1];
    }
  }
};

jQuery(document).ready(function(){
  var search = '<?php echo get_search_query(); ?>';
  var fromsearch = '<?php $output = '';
if(isset($_GET['fromsearch']) && is_string($_GET['fromsearch'])) {
$output = $_GET['fromsearch'];
}
echo $output; ?>'; 

  if(search !== null && search !== ''){ 
   jQuery('body').highlight(search,'highlight');
      jQuery('#main article a').each(function(i,e){
        var newUrl =  jQuery(e).prop('href') + '?fromsearch=' + encodeURIComponent(search);
        this.href = newUrl;
      });
   }
   
   if(fromsearch !== null && fromsearch !== ''){
      jQuery('body').highlight(fromsearch,'highlight');
   }
});
</script>