If you are using jsTree library and found out that Chrome has started to warn about deprecating a feature used by jstree like below. Then you can find what you need to do to resolve this issue (warning).
document.registerElement is deprecated and will be removed in M73, around March 2019. Please use window.customElements.define instead. See https://www.chromestatus.com/features/4642138092470272 for more details.
You are still receiving this warning that means your jsTree js file is old and you haven't updated it for long time.
This issue has already been fixed in latest jsTree library. So you do not need to make any changes in your code, just upgrade the your jsTree js file i.e. jstree.min.js.
Please update jstree library to 3.3.7 onwards. Current version is 3.3.8. You can download it from https://github.com/vakata/jstree or use following CDN:
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script> <link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/jstree/3.3.8/themes/default/style.min.css" /> <script src="//cdnjs.cloudflare.com/ajax/libs/jstree/3.3.8/jstree.min.js"></script>