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chromium/third_party/blink/web_tests/editing/inserting/typing_ligature_at_start.html 

<!doctype html>
<style>
div {
  border: solid 1px pink;
  font-size: 60px;
  padding: 5px;
  direction: rtl;
}
</style>
<div id="sample1">&#x628;&#x647; &#x628;&#x647;</div>
<div id="sample2">AV AV</div>
<br>
<div id="target1">&#x647; &#x647;</div>
<div id="target2">V V</div>
<script>
function forceLayout() { document.body.offsetHeight; }
const target1 = document.getElementById('target1');
const target2 = document.getElementById('target2');
const text1 = target1.firstChild;
const text2 = target2.firstChild;
forceLayout();
text1.insertData(0, '\u0628');
text2.insertData(0, 'A');
forceLayout();
text1.insertData(3, '\u0628');
text2.insertData(3, 'A');
</script>