JSFiddle - React, Tailwind, and code Playground

HTML

<textarea id="test" rows="10" cols="50">one
two
three</textarea>

<pre>"wo
th" should be selected</pre>

JavaScript

function adjustOffset(el, offset) {
    var val = el.value, newOffset = offset;
    if (val.indexOf("\r\n") > -1) {
        var matches = val.replace(/\r\n/g, "\n").slice(0, offset).match(/\n/g);
        newOffset += matches ? matches.length : 0;
    }
    return newOffset;
};

setCaretToPos = function(input, selectionStart, selectionEnd){
  input.focus();
  if(input.setSelectionRange){
    selectionStart = adjustOffset(input, selectionStart);
    selectionEnd = adjustOffset(input, selectionEnd);
    input.setSelectionRange(selectionStart, selectionEnd);

  }else if(input.createTextRange){
    var range = input.createTextRange();
    range.collapse(true);
    range.moveEnd('character', selectionEnd);
    range.moveStart('character', selectionStart);
    range.select();
  }
};

setCaretToPos(document.getElementById("test"), 5, 10);