<!doctype html>
<meta charset=utf-8>
<!-- Our target div should be placed as if it were a child of the overflowing --
  -- thing; this is simplest to accomplish by just having the overflowing thing --
  -- absolutely positioned so the target div is placed as if it were not there -->
<div style="overflow: auto; height: 100px; width: 200px; position: absolute">
  <div style="width: 400px; height: 10px"></div>
</div>
<div id="target">Modified text</div>
<script>
  document.querySelector("div").scrollLeft = 1000;
</script>