How can I get the positions of regex matches in ClojureScript?

Question

In Clojure I could use something like this solution: Compact Clojure code for regular expression matches and their position in string, i.e., creating a re-matcher and extracted the information from that, but re-matcher doesn't appear to be implemented in ClojureScript. What would be a good way to accomplish the same thing in ClojureScript?

Edit:

I ended up writing a supplementary function in order to preserve the modifiers of the regex as it is absorbed into re-pos:

(defn regex-modifiers
  "Returns the modifiers of a regex, concatenated as a string."
  [re]
  (str (if (.-multiline re) "m")
       (if (.-ignoreCase re) "i")))

(defn re-pos
  "Returns a vector of vectors, each subvector containing in order:
   the position of the match, the matched string, and any groups
   extracted from the match."
  [re s]
  (let [re (js/RegExp. (.-source re) (str "g" (regex-modifiers re)))]
    (loop [res []]
      (if-let [m (.exec re s)]
        (recur (conj res (vec (cons (.-index m) m))))
        res))))

Answer 1

You can use the .exec method of JS RegExp object. The returned match object contains an index property that corresponds to the index of the match in the string.

Currently clojurescript doesn't support constructing regex literals with the g mode flag (see CLJS-150), so you need to use the RegExp constructor. Here is a clojurescript implementation of the re-pos function from the linked page:

(defn re-pos [re s]
  (let [re (js/RegExp. (.-source re) "g")]
    (loop [res {}]
      (if-let [m (.exec re s)]
        (recur (assoc res (.-index m) (first m)))
        res))))

cljs.user> (re-pos "\\w+" "The quick brown fox")
{0 "The", 4 "quick", 10 "brown", 16 "fox"}
cljs.user> (re-pos "[0-9]+" "3a1b2c1d")
{0 "3", 2 "1", 4 "2", 6 "1"}