var htmlString = '<meta http-equiv="Set-Cookie" content="COOKIE1_VALUE_HERE">\n'+

'<meta http-equiv="Set-Cookie" content="COOKIE2_VALUE_HERE">\n'+

'<meta http-equiv="Set-Cookie" content="COOKIE3_VALUE_HERE">\n';

​

var setCookieMetaRegExp = /<meta http-equiv=[\"']?set-cookie[\"']? content=[\"'](.*)[\"'].*>/ig;

​

var matches = [];

while (setCookieMetaRegExp.exec(htmlString)) {

  matches.push(RegExp.$1);

}

​

console.log(matches);