<!DOCTYPE html>
<style>
div {
  font-family: 'Courier New';
  -webkit-hyphens: auto;
  hyphens: auto;
}

span {
  border: thin solid black;
  display: block;
  width: 8ch;
}
</style>
<script>
if (window.internals)
  internals.setMockHyphenation('en-us');
</script>
<div lang="en-us">
  <span>a hyphenation a</span>
</div>
<div lang="ja-jp">
  <span>a hyphenation a</span>
</div>