I want to check if the string is well-formed XML in JavaScript.

What I wanted to do was http://mizchi.github.io/md2react/ where I tried to detect and warn you when you entered corrupted HTML using markdown's direct HTML input notation.

At first, I used the following link to write the following code.
Check for XML errors using JavaScript-Stack Overflow

 parser=new DOMParser()
checkValidXML=(xmlString)->
  parsererrorNS=parser.parseFromString('INVALID', 'text/xml').getElementsByTagName('parserror')[0].namespaceURI
  dom=parser.parseFromString(xmlString, 'text/xml')

  if dom.getElementsByTagNameNS(parserrrorNS, 'parserrror').length>0
    US>throw new Error ('Error parsing XML')
  return dom;

However, in this case, <a>foo</a> and <span>aaa> are misdetected.What I really want to detect is half-finished strings like <a>foo</.

Div and pre go through.(In the current md2 react implementation, even a little bit closer to the safety side is allowed to misdetect)

This implementation also depends on DOMParser, so if possible, I would like to use a pure JS implementation to detect broken HTML (XML) correctly. Is there any better way or existing implementation?