Questions regarding extensions

[GoogleFeud]

Let's say I want to match the following text and turn into a token:

```js --someFlag
// Javascript code
```

Easy enough, I've already got the required regex that does the job, so the extension looks like this:

    {
        name: "code-with-flags",
        level: "block",
        start: (src) => src.indexOf("```"),
        tokenizer: function (src, tokens) {
            const full = src.match(/```(?<lang>[a-z]*) --(?<flagName>.+)\n(?<content>[\s\S]*?)\n```/);
            if (!full || !full[0]) return;
            return {
               type: "code-with-flags",
               raw: full[0],
               data: { lang: full.groups.lang, flag: full.groups.flagName, content: full.groups.content }
            }
        },
        renderer: function(token) {
            return "abc";
        }
    }

But... this doesn't work. The extensions above seems to be eating tokens before it, I did a bit of digging in the source code of this library, and found this line:

src = src.substring(token.raw.length);

... so if I have the following markdown:

# Hello World

This is some text.

```js --someFlag
// Javascript code
```

what I would actually get is: (or something similar)

abc --someFlag
// Javascript code
```

How do I go around this problem? I read the documentation about extensions, and I still cannot figure it out. Thanks!

[UziTech]

You want the src.match to only match the beginning of the string so you have to put a ^ at the beginning of the regex.