JSFiddle - React, Tailwind, and code Playground

JavaScript

var ows_MetaInfo="1;#Subject:SW|NameOfADocument\n\
vti_parservers:SR|23.0.0.6421\n\
ContentTypeID:SW|0x0101001DB26Cf25E4F31488B7333256A77D2C\n\
vti_cachedtitle:SR|NameOfADocument\n\
vti_title:SR|ATitleOfADocument\n\
_Author:SW:|TheNameOfOurCompany\n\
_Category:SW|\n\
ContentType:SW|Document\n\
vti_author::SR|mrwienerdog\n\
_Comments:SW|This is very much the string I need extracted\n\
vti_categories:VW|\n\
vtiapprovallevel:SR|\n\
vti_modifiedby:SR|mrwienerdog\n\
vti_assignedto:SR|\n\
Keywords:SW|Project Name\n\
ContentType _Comments";

console.log("original input:\n" + ows_MetaInfo);
var matchresult = ows_MetaInfo.match(/^_Comments:SW\|(.*)$/m);
var comment = (matchresult==null) ? "" : matchresult[1];
console.log("RESULT:" + comment);