From b0c8b9dcd5459b444f03f1b28e660756f3355862 Mon Sep 17 00:00:00 2001
From: Christian-Bermejo <Christian_Bermejo@trendmicro.com>
Date: Sun, 14 Jun 2026 07:47:22 +0800
Subject: [PATCH] Cache compiled emoji regexes in countEmoji
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countEmoji recompiled one RegExp per emoji (~70) on every call, and it runs once
per tweet across several call sites (enrich, analyzeSentiment, analyzeTone) — so a
large CSV recompiled hundreds of thousands of throwaway regexes.

Compile each list's regexes once and cache them in a WeakMap keyed on the list
array (POSITIVE_EMOJI / NEGATIVE_EMOJI are stable module constants, so they compile
once total). Counting semantics are unchanged: same per-emoji regex + 'g' flag, and
String.prototype.match with /g is stateless (resets lastIndex), so reusing the
compiled regexes across calls is safe.

Adds a repeated-call regression test. Build + 41 tests green.
---
 studio/src/lib/analysis.js      | 20 ++++++++++++++++++--
 studio/src/lib/analysis.test.js |  7 +++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/studio/src/lib/analysis.js b/studio/src/lib/analysis.js
index 6280729..79527ac 100644
--- a/studio/src/lib/analysis.js
+++ b/studio/src/lib/analysis.js
@@ -21,10 +21,26 @@ export function tokenize(text) {
     .filter(Boolean);
 }
 
+// Compiled emoji regexes are cached per emoji-list array so countEmoji does not
+// recompile ~70 RegExps on every call (it runs once per tweet, several times).
+// String.prototype.match with a /g regex is stateless (it ignores and resets
+// lastIndex), so reusing the same compiled regexes across calls is safe.
+const _emojiRegexCache = new WeakMap();
+
+function emojiRegexes(list) {
+  let regexes = _emojiRegexCache.get(list);
+  if (!regexes) {
+    regexes = list.map(
+      (e) => new RegExp(e.replace(/[-\/\\^$*+?.()|[\]{}]/g, "\\$&"), "g"),
+    );
+    _emojiRegexCache.set(list, regexes);
+  }
+  return regexes;
+}
+
 export function countEmoji(text, list) {
   let count = 0;
-  for (const e of list) {
-    const re = new RegExp(e.replace(/[-\/\\^$*+?.()|[\]{}]/g, "\\$&"), "g");
+  for (const re of emojiRegexes(list)) {
     const m = text.match(re);
     if (m) count += m.length;
   }
diff --git a/studio/src/lib/analysis.test.js b/studio/src/lib/analysis.test.js
index 111d8f7..b21a0ca 100644
--- a/studio/src/lib/analysis.test.js
+++ b/studio/src/lib/analysis.test.js
@@ -35,6 +35,13 @@ describe("countEmoji", () => {
   it("returns 0 when no listed emoji are present", () => {
     expect(countEmoji("plain text", POSITIVE_EMOJI)).toBe(0);
   });
+
+  it("stays correct across repeated calls with the same list (cached regexes are stateless)", () => {
+    expect(countEmoji("🔥🔥", POSITIVE_EMOJI)).toBe(2);
+    expect(countEmoji("🔥", POSITIVE_EMOJI)).toBe(1);
+    expect(countEmoji("no emoji here", POSITIVE_EMOJI)).toBe(0);
+    expect(countEmoji("🔥🔥🔥", POSITIVE_EMOJI)).toBe(3);
+  });
 });
 
 describe("analyzeSentiment", () => {