How to replace with font awesome

I'd really like to replace this heart image with font awesome, but I don't know how.

Code:

function VLIKE(b,a){
  a.onclick="#";
    $.get(b,function(){
    a.parentNode.style.display='none';
    a.parentNode.nextSibling.firstChild.className='positive';
    var c=a.parentNode.nextSibling.firstChild,
    b=parseInt(/\d+/.exec(c.innerHTML)[0])+1;
    c.innerHTML=c.innerHTML.replace(/\d+/,b);
    }
)};
$(function(){
var x = $('.vote').get();
for(i = x.length-1; i >= 0; i--){
  var numb = '0';

  var reputation_UP = 'http://twemoji.maxcdn.com/72x72/2764.png';

  var button = $(x[i]).find('.vote-button a').get();
  for(j=0; j < button.length; j++){
    if(button[j].innerHTML == '+'){
      reputation_UP = '<span onclick="VLIKE(\'' + button[j].href + '\',this);"><img src="'+reputation_UP+'" alt="+" class="rep_up"></span>';
    }
  }
  var bar = $(x[i]).find('.vote-bar')[0];
  if(bar){
      var s = bar.title.split(' ');
      var pct = parseInt(s[3].replace(/%/,''))/100;
      var num = parseInt(s[4].replace(/\(/,''));
      numb = String(Math.round(num*pct));
      reputation_UP = '<img src="'+reputation_UP+'" alt="+" class="rep_up">';
  }
    var votetext = numb;
    var Html = '<div class="rep_bar clearfix" id="rep_post">
                          <ul class="bs_inline">
                              <li>'+reputation_UP+'</li>
                              <li><span id="reput_vote">'+votetext+'</span></li>
                          </ul>
                        </div>';
$(x[i].parentNode.parentNode.parentNode.parentNode).find('.postfoot').before(Html);
  if(!bar){
$(x[i].parentNode.parentNode.parentNode.parentNode).find('#reput_vote').addClass('zero');
  }else{
$(x[i].parentNode.parentNode.parentNode.parentNode).find('#reput_vote').addClass('positive');
$(x[i].parentNode.parentNode.parentNode.parentNode).find('.rep_up').parents('li').css({"display":"none"});
  }
  x[i].parentNode.removeChild(x[i]);
}
});

I'd like to add this:

Code:

<font size="3px"><font color="red"><i class="fa fa-heart" aria-hidden="true"></i></font>

Instead of this:

Code:

var reputation_UP = 'http://twemoji.maxcdn.com/72x72/2764.png';

Can somebody send me the fix to this code to make it work properly, thanks.

hello

change this 

Code:

var reputation_UP = 'http://twemoji.maxcdn.com/72x72/2764.png';

with this 

Code:

var reputation_UP = 'https://i37.servimg.com/u/f37/11/40/02/06/1235.png';