Best way to override renderer rules?

I’m working on something where users can use markdown. I’d like for all of the links to open in a new window. The following code works, but is this the best way to achieve this?

var md = new markdownit("default", {
    breaks: true, linkify: true, typographer: true
});
//Override link render to open all link in a new window
md.renderer.rules.link_open = (tokens, idx) => {
    var title = tokens[idx].title ? (' title="' + md.utils.escapeHtml(md.utils.replaceEntities(tokens[idx].title)) + '"') : '';
    return '<a href="' + md.utils.escapeHtml(tokens[idx].href) + '"' + title + ' target="_blank">';
};

I also want to allow fenced code to have a simpler syntax where you don’t need to have the triple backticks on their own lines. Input example would be:

```for (var i = 0; i <= items.length; i++) {
  console.log(i);
}```

How can I achieve this? Right now I’ve got a hacky partial solution where it treats the language parameter as the first line of code, but the last line isn’t seen.

//allow simpler fenced code
md.renderer.rules.fence = (tokens, idx, options) => {
    var token = tokens[idx];
    console.log(token)
    return '<pre>'
        + md.utils.escapeHtml(token.params+"\n" +token.content)
        + '</pre>\n';
};

I know this isn’t a good solution, and it seems like md.renderer.rules.fence isn’t the right place to do this sort of thing. How can I achieve this?

[puzrin]

That’s full logic, can be reduced:

val old_render = md.renderer.rules.link_open || function(tokens, idx, options, env, self) {
  return self.renderToken(tokens, idx, options);
};

md.renderer.rules.link_open = (tokens, idx, options, env, self) => {
  token[idx].attrPush(['target', '_blank']);

  return old_render(tokens, idx, options, env, self);
};

Or patch attributes in core chain:

https://github.com/markdown-it/markdown-it-for-inline#use (example 3)

[caub]

Yes thanks, I’ve seen that link 5 messages up, I’ll look in the code too