is-html 
Check if a string is HTML
You should not use this for any kind of validation, sanitation, or XSS checks.
Install
$ npm install is-html
Usage
const isHtml = require('is-html');
isHtml('<p>I am HTML</p>');
//=> true
isHtml('<!doctype><html><body><h1>I ❤ unicorns</h1></body></html>');
//=> true
isHtml('<cake>I am XML</cake>');
//=> false
isHtml('>+++++++>++++++++++>+++>+<<<<-');
//=> falseNote: It does not detect deprecated HTML tags.