<!DOCTYPE html>
<html>
<head>
<style>
#editable { zoom: 250%; }
</style>
<script>
function runTest() {
const editable = document.getElementById("editable");
getSelection().selectAllChildren(editable);
if (window.internals) {
const range = document.createRange();
range.setStart(editable.firstChild, 0);
range.setEnd(editable.firstChild, 8);
internals.setMarker(document, range, 'spelling');
}
}
</script>
</head>
<body onload="runTest();">
<div id="editable" contenteditable="true">wellcome should be marked</div>
</body>
</html>