JavaScript regular expression extracts child matches __ regular expressions

The regular expression used in C #, if you want to extract the child matches in the string (I don't know what the name is, alias.) ) is very convenient, for example:

Regex rx = new Regex (@ "<title> <title>[\s\s]+)?</title>", regexoptions.compiled | Regexoptions.ignorecase);
Match m = Rx. Match (content);
if (m.success)
{
    string title = M.result ("${title}");
}

But if it's JavaScript, how about the whole thing? The syntax on both sides seems slightly different. I got it down, and there were only a few fragments of empirical values that were recorded first:

str = " 
Reference articles:
http://www.html-js.com/article/3420