JSFiddle - React, Tailwind, and code Playground

HTML

<textarea id="textarea"></textarea>

JavaScript

function doubleCarriage(id){
    var a = document.getElementById(id);
    a.addEventListener('keypress',function(e){
        if(e.which == 13 || e.keyCode == 13 ) {
            e.preventDefault();
            var caret = getCaret(a);
            var length = a.value.length;
            a.value = a.value.substring(0, caret) + "\n\n" + a.value.substring(caret + 1, length);
        }
    });
}

function getCaret(el) { 
  if (el.selectionStart) { 
    return el.selectionStart; 
  } else if (document.selection) { 
    el.focus(); 

    var r = document.selection.createRange(); 
    if (r == null) { 
      return 0; 
    } 

    var re = el.createTextRange(), 
        rc = re.duplicate(); 
    re.moveToBookmark(r.getBookmark()); 
    rc.setEndPoint('EndToStart', re); 

    return rc.text.length; 
  }  
  return 0; 
}

doubleCarriage("textarea");