strings.FindRESubmatch

By default, findRESubmatch finds all matches. You can limit the number of matches with an optional LIMIT argument. A return value of nil indicates no match.

Demonstrative examples

{{ findRESubmatch `a(x*)b` "-ab-" }} → [["ab" ""]]
{{ findRESubmatch `a(x*)b` "-axxb-" }} → [["axxb" "xx"]]
{{ findRESubmatch `a(x*)b` "-ab-axb-" }} → [["ab" ""] ["axb" "x"]]
{{ findRESubmatch `a(x*)b` "-axxb-ab-" }} → [["axxb" "xx"] ["ab" ""]]
{{ findRESubmatch `a(x*)b` "-axxb-ab-" 1 }} → [["axxb" "xx"]]

Practical example

This Markdown:

- [Example](https://example.org)
- [Hugo](https://gohugo.io)

Produces this HTML:

<ul>
  <li><a href="https://example.org">Example</a></li>
  <li><a href="https://gohugo.io">Hugo</a></li>
</ul>

To match the anchor elements, capturing the link destination and text:

{{ $regex := `<a\s*href="(.+?)">(.+?)</a>` }}
{{ $matches := findRESubmatch $regex .Content }}

Viewed as JSON, the data structure of $matches in the code above is:

[
  [
    "<a href=\"https://example.org\"></a>Example</a>",
    "https://example.org",
    "Example"
  ],
  [
    "<a href=\"https://gohugo.io\">Hugo</a>",
    "https://gohugo.io",
    "Hugo"
  ]
]

To render the href attributes:

{{ range $matches }}
  {{ index . 1 }}
{{ end }}

Result:

https://example.org
https://gohugo.io

You can write and test your regular expression using regex101.com. Be sure to select the Go flavor before you begin.