JSFiddle - React, Tailwind, and code Playground

HTML

<textarea id="textarea">
    Some sample text.
    <img src="" alt="">
    More text
    <img src="" alt="">
</textarea>
<br>
<a onclick="nextAlt($('#textarea'));">Next</a>

CSS

textarea {
    width: 400px;
    height: 200px;
}

JavaScript

function setSelectionRange(input, selectionStart, selectionEnd) {
  if (input.setSelectionRange) {
    input.focus();
    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();
  }
}

function setCaretToPos (input, pos) {
  setSelectionRange(input, pos, pos);
}

function nextAlt(input) {
    pos = input.val().indexOf('alt=""');
    if (-1 == pos) {
        alert("None found");
    } else {
        setCaretToPos(input.get(0), pos);
    }
}