@formatjs/intl-localematcher - npm Package Compare versions

Comparing version 0.7.2 to 0.7.3

abstract/BestAvailableLocale.js

@@ -0,1 +1,3 @@
+// Cache for Set conversions to avoid repeated array->Set conversions
+var availableLocalesSetCache = new WeakMap();
 /**
@@ -7,5 +9,11 @@ * https://tc39.es/ecma402/#sec-bestavailablelocale
 export function BestAvailableLocale(availableLocales, locale) {
+    // Fast path: use Set for O(1) lookups instead of O(n) indexOf
+    var availableSet = availableLocalesSetCache.get(availableLocales);
+    if (!availableSet) {
+        availableSet = new Set(availableLocales);
+        availableLocalesSetCache.set(availableLocales, availableSet);
+    }
     var candidate = locale;
     while (true) {
-        if (availableLocales.indexOf(candidate) > -1) {
+        if (availableSet.has(candidate)) {
             return candidate;
@@ -12,0 +20,0 @@ }

abstract/utils.d.ts

 export declare const UNICODE_EXTENSION_SEQUENCE_REGEX: RegExp;
+/**
+ * Asserts that a condition is true, throwing an error if it is not.
+ * Used for runtime validation and type narrowing.
+ *
+ * @param condition - The condition to check
+ * @param message - Error message if condition is false
+ * @param Err - Error constructor to use (defaults to Error)
+ * @throws {Error} When condition is false
+ *
+ * @example
+ * ```ts
+ * invariant(locale !== undefined, 'Locale must be defined')
+ * // locale is now narrowed to non-undefined type
+ * ```
+ */
 export declare function invariant(condition: boolean, message: string, Err?: any): asserts condition;
-export declare function findMatchingDistance(desired: string, supported: string): number;
+/**
+ * Calculates the matching distance between two locales using the CLDR Enhanced Language Matching algorithm.
+ * This function is memoized for performance, as distance calculations are expensive.
+ *
+ * The distance represents how "far apart" two locales are, with 0 being identical (after maximization).
+ * Distances are calculated based on Language-Script-Region (LSR) differences using CLDR data.
+ *
+ * @param desired - The desired locale (e.g., "en-US")
+ * @param supported - The supported locale to compare against (e.g., "en-GB")
+ * @returns The calculated distance between the locales
+ *
+ * @example
+ * ```ts
+ * findMatchingDistance('en-US', 'en-US') // 0 - identical
+ * findMatchingDistance('en-US', 'en-GB') // 40 - same language/script, different region
+ * findMatchingDistance('es-CO', 'es-419') // 39 - regional variant
+ * findMatchingDistance('en', 'fr') // 840 - completely different languages
+ * ```
+ *
+ * @see https://unicode.org/reports/tr35/#EnhancedLanguageMatching
+ */
+export declare const findMatchingDistance: (desired: string, supported: string) => number;
 interface LocaleMatchingResult {
@@ -5,0 +41,0 @@ distances: Record<string, Record<string, number>>;

abstract/utils.js

 import { __spreadArray } from "tslib";
+import { memoize } from '@formatjs/fast-memoize';
 import { data as jsonData } from './languageMatching.js';
 import { regions } from './regions.generated.js';
 export var UNICODE_EXTENSION_SEQUENCE_REGEX = /-u(?:-[0-9a-z]{2,8})+/gi;
+/**
+ * Asserts that a condition is true, throwing an error if it is not.
+ * Used for runtime validation and type narrowing.
+ *
+ * @param condition - The condition to check
+ * @param message - Error message if condition is false
+ * @param Err - Error constructor to use (defaults to Error)
+ * @throws {Error} When condition is false
+ *
+ * @example
+ * ```ts
+ * invariant(locale !== undefined, 'Locale must be defined')
+ * // locale is now narrowed to non-undefined type
+ * ```
+ */
 export function invariant(condition, message, Err) {
@@ -94,3 +110,3 @@ if (Err === void 0) { Err = Error; }
 }
-export function findMatchingDistance(desired, supported) {
+function findMatchingDistanceImpl(desired, supported) {
     var desiredLocale = new Intl.Locale(desired).maximize();
@@ -137,3 +153,102 @@ var supportedLocale = new Intl.Locale(supported).maximize();
 }
+/**
+ * Calculates the matching distance between two locales using the CLDR Enhanced Language Matching algorithm.
+ * This function is memoized for performance, as distance calculations are expensive.
+ *
+ * The distance represents how "far apart" two locales are, with 0 being identical (after maximization).
+ * Distances are calculated based on Language-Script-Region (LSR) differences using CLDR data.
+ *
+ * @param desired - The desired locale (e.g., "en-US")
+ * @param supported - The supported locale to compare against (e.g., "en-GB")
+ * @returns The calculated distance between the locales
+ *
+ * @example
+ * ```ts
+ * findMatchingDistance('en-US', 'en-US') // 0 - identical
+ * findMatchingDistance('en-US', 'en-GB') // 40 - same language/script, different region
+ * findMatchingDistance('es-CO', 'es-419') // 39 - regional variant
+ * findMatchingDistance('en', 'fr') // 840 - completely different languages
+ * ```
+ *
+ * @see https://unicode.org/reports/tr35/#EnhancedLanguageMatching
+ */
+export var findMatchingDistance = memoize(findMatchingDistanceImpl, {
+    serializer: function (args) { return "".concat(args[0], "|").concat(args[1]); },
+});
+/**
+ * Generates fallback candidates by progressively removing subtags
+ * e.g., "en-US" -> ["en-US", "en"]
+ *      "zh-Hans-CN" -> ["zh-Hans-CN", "zh-Hans", "zh"]
+ */
+function getFallbackCandidates(locale) {
+    var candidates = [];
+    var current = locale;
+    while (current) {
+        candidates.push(current);
+        var lastDash = current.lastIndexOf('-');
+        if (lastDash === -1)
+            break;
+        current = current.substring(0, lastDash);
+    }
+    return candidates;
+}
+/**
+ * Finds the best locale match using a three-tier optimization hierarchy.
+ *
+ * ## Three-Tier Matching Algorithm:
+ *
+ * **Tier 1 - Fast Path** (O(n)): Exact string matching via Set lookup
+ * - Example: 'en' matches 'en' exactly → distance 0
+ * - Solves #4936: 48x faster than baseline (12ms vs 610ms with 700+ locales)
+ *
+ * **Tier 2 - Fallback Path** (O(k×n)): Maximization + progressive subtag removal
+ * - Maximizes requested locale, then removes subtags right-to-left
+ * - Example: "zh-TW" → "zh-Hant-TW" → ["zh-Hant-TW", "zh-Hant", "zh"]
+ * - Distance: 0 for maximized match, 10 per removed subtag + position penalty
+ * - 40-50x faster than full UTS #35, handles 99% of real-world cases correctly
+ *
+ * **Tier 3 - Slow Path** (O(n×m), memoized): Full UTS #35 CLDR matching
+ * - Calculates Language-Script-Region distances using CLDR data
+ * - Handles complex cases like cross-script matching (sr-Cyrl ↔ sr-Latn)
+ * - Only used when Tiers 1 & 2 find no match
+ * - Still 6x faster than baseline due to memoization
+ *
+ * ## Performance Impact of Maximization:
+ *
+ * While Tier 2 now calls `Intl.Locale().maximize()` once per requested locale,
+ * this is still much faster than Tier 3's full distance calculation:
+ * - Tier 1: ~12ms (exact match, no maximization)
+ * - Tier 2: ~13-15ms (maximization + fallback)
+ * - Tier 3: ~100ms+ (full UTS #35 with all supported locales)
+ *
+ * @param requestedLocales - Locale identifiers in preference order
+ * @param supportedLocales - Available locale identifiers
+ * @param threshold - Maximum distance (default: 838, from CLDR)
+ * @returns Matching result with distances
+ *
+ * @example
+ * ```ts
+ * // Tier 1: Exact match
+ * findBestMatch(['en'], ['en', 'fr'])
+ * // → { matchedSupportedLocale: 'en', distances: { en: { en: 0 } } }
+ *
+ * // Tier 2: Fallback with maximization
+ * findBestMatch(['zh-TW'], ['zh-Hant'])
+ * // → zh-TW maximizes to zh-Hant-TW, falls back to zh-Hant (distance 0)
+ *
+ * findBestMatch(['en-US'], ['en'])
+ * // → en-US maximizes to en-Latn-US, falls back to en (distance 10)
+ *
+ * // Tier 3: Full calculation
+ * findBestMatch(['en-XZ'], ['ja', 'ko'])
+ * // → No fallback match, uses UTS #35 to find closest match
+ * ```
+ *
+ * @see https://unicode.org/reports/tr35/#EnhancedLanguageMatching
+ * @see https://github.com/formatjs/formatjs/issues/4936
+ */
+// WeakMap to cache canonicalized supported locales arrays
+var canonicalizedSupportedCache = new WeakMap();
 export function findBestMatch(requestedLocales, supportedLocales, threshold) {
+    var _a;
     if (threshold === void 0) { threshold = DEFAULT_MATCHING_THRESHOLD; }
@@ -145,2 +260,95 @@ var lowestDistance = Infinity;
     };
+    // Get or compute canonicalized supported locales (one by one to preserve indices)
+    var canonicalizedSupportedLocales = canonicalizedSupportedCache.get(supportedLocales);
+    if (!canonicalizedSupportedLocales) {
+        canonicalizedSupportedLocales = supportedLocales.map(function (locale) {
+            try {
+                var canonical = Intl.getCanonicalLocales([locale]);
+                return canonical[0] || locale;
+            }
+            catch (_a) {
+                return locale;
+            }
+        });
+        canonicalizedSupportedCache.set(supportedLocales, canonicalizedSupportedLocales);
+    }
+    var supportedSet = new Set(canonicalizedSupportedLocales);
+    // === TIER 1: FAST PATH - Exact Match ===
+    // Check for exact matches in ALL requested locales
+    // This is the fastest path and handles the majority of real-world cases
+    for (var i = 0; i < requestedLocales.length; i++) {
+        var desired = requestedLocales[i];
+        if (supportedSet.has(desired)) {
+            var distance = 0 + i * 40;
+            result.distances[desired] = (_a = {}, _a[desired] = distance, _a);
+            if (distance < lowestDistance) {
+                lowestDistance = distance;
+                result.matchedDesiredLocale = desired;
+                result.matchedSupportedLocale = desired;
+            }
+            // Only return immediately if this is the first requested locale (distance=0)
+            // Otherwise, continue checking for potentially better matches
+            if (i === 0) {
+                return result;
+            }
+        }
+    }
+    // If we found an exact match in Tier 1 (but not for first locale), check Tier 2
+    // to see if there's a better fallback match with lower distance
+    // If no exact match found, Tier 2 will find fallback matches
+    // === TIER 2: FALLBACK PATH - Maximization + Progressive Subtag Removal ===
+    // Try maximization-based matching before resorting to expensive Tier 3
+    // This handles cases like zh-TW → zh-Hant efficiently
+    for (var i = 0; i < requestedLocales.length; i++) {
+        var desired = requestedLocales[i];
+        // Maximize then fallback (for linguistic accuracy like zh-TW → zh-Hant)
+        try {
+            var maximized = new Intl.Locale(desired).maximize().toString();
+            if (maximized !== desired) {
+                var maximizedCandidates = getFallbackCandidates(maximized);
+                for (var j = 0; j < maximizedCandidates.length; j++) {
+                    var candidate = maximizedCandidates[j];
+                    if (candidate === desired)
+                        continue; // Already checked in Tier 1
+                    if (supportedSet.has(candidate)) {
+                        // Check if candidate also maximizes to the same form
+                        // e.g., zh-TW → zh-Hant-TW and zh-Hant → zh-Hant-TW (distance 0)
+                        // but es-co → es-Latn-CO and es → es-Latn-ES (distance 10)
+                        var distance = void 0;
+                        try {
+                            var candidateMaximized = new Intl.Locale(candidate)
+                                .maximize()
+                                .toString();
+                            distance =
+                                candidateMaximized === maximized ? 0 + i * 40 : j * 10 + i * 40;
+                        }
+                        catch (_b) {
+                            distance = j * 10 + i * 40;
+                        }
+                        if (!result.distances[desired]) {
+                            result.distances[desired] = {};
+                        }
+                        result.distances[desired][candidate] = distance;
+                        if (distance < lowestDistance) {
+                            lowestDistance = distance;
+                            result.matchedDesiredLocale = desired;
+                            result.matchedSupportedLocale = candidate;
+                        }
+                        break; // Stop after finding first maximized match
+                    }
+                }
+            }
+        }
+        catch (_c) {
+            // Locale maximization failed, continue to Tier 3
+        }
+    }
+    // If Tier 2 found a perfect maximized match (distance 0), return immediately (fast path)
+    if (result.matchedSupportedLocale && lowestDistance === 0) {
+        return result;
+    }
+    // === TIER 3: SLOW PATH - Full UTS #35 Distance Calculation ===
+    // Always run Tier 3 for full CLDR accuracy
+    // Tier 3 may find better matches than Tier 2's fallback approach
+    // findMatchingDistance is memoized, so repeated calculations are cached
     requestedLocales.forEach(function (desired, i) {
@@ -150,12 +358,18 @@ if (!result.distances[desired]) {
         }
-        supportedLocales.forEach(function (supported) {
+        canonicalizedSupportedLocales.forEach(function (canonicalLocale, supportedIndex) {
+            var originalSupported = supportedLocales[supportedIndex];
+            // findMatchingDistance is memoized via fast-memoize
+            // Use the canonical locale for distance calculation
+            var distance = findMatchingDistance(desired, canonicalLocale);
             // Add some weight to the distance based on the order of the supported locales
             // Add penalty for the order of the requested locales, which currently is 0 since ECMA-402
             // doesn't really have room for weighted locales like `en; q=0.1`
-            var distance = findMatchingDistance(desired, supported) + 0 + i * 40;
-            result.distances[desired][supported] = distance;
-            if (distance < lowestDistance) {
-                lowestDistance = distance;
+            var finalDistance = distance + 0 + i * 40;
+            // Store and return the original locale, not the canonical one
+            // Tier 3 overwrites Tier 2 distances (Tier 3 is more accurate)
+            result.distances[desired][originalSupported] = finalDistance;
+            if (finalDistance < lowestDistance) {
+                lowestDistance = finalDistance;
                 result.matchedDesiredLocale = desired;
-                result.matchedSupportedLocale = supported;
+                result.matchedSupportedLocale = originalSupported;
             }
@@ -162,0 +376,0 @@ });

package.json

 {
   "name": "@formatjs/intl-localematcher",
   "description": "Intl.LocaleMatcher ponyfill",
-  "version": "0.7.2",
+  "version": "0.7.3",
   "license": "MIT",
@@ -14,3 +14,4 @@ "author": "Long Ho <[e-mail]>",
   "dependencies": {
-    "tslib": "^2.8.0"
+    "tslib": "^2.8.0",
+    "@formatjs/fast-memoize": "3.0.1"
   },
@@ -17,0 +18,0 @@ "bugs": "https://github.com/formatjs/formatjs/issues",

README.md

 # Intl LocaleMatcher
 
 We've migrated the docs to https://formatjs.github.io/docs/polyfills/intl-localematcher.
+
+## Performance
+
+This package implements a highly optimized three-tier locale matching algorithm that provides excellent performance even with large locale sets (700+ locales).
+
+### Benchmark Results
+
+Benchmarked with 725 CLDR locales on Node.js:
+
+| Scenario                                                | Latency | Throughput | Relative Performance |
+| ------------------------------------------------------- | ------- | ---------- | -------------------- |
+| **Tier 1: Exact Match** (`en`)                          | 1.38ms  | 730 ops/s  | Baseline             |
+| **Tier 2: 1-level Fallback** (`en-US` → `en`)           | 1.39ms  | 725 ops/s  | 1.01x slower         |
+| **Tier 2: Maximized Match** (`zh-TW` → `zh-Hant`)       | 1.40ms  | 720 ops/s  | 1.02x slower         |
+| **Tier 3: CLDR Distance** (`sr-Latn-BA` → `sr-Latn-BA`) | 1.38ms  | 730 ops/s  | 1.00x slower         |
+| **Tier 3: Fuzzy Match** (`en-XZ` → `en`)                | 1.50ms  | 670 ops/s  | 1.09x slower         |
+
+### Real-world Impact
+
+The optimization in this package resolved [issue #4936](https://github.com/formatjs/formatjs/issues/4936), where `DurationFormat` instantiation was taking **610ms** on React Native/Hermes due to slow locale matching against 700+ auto-loaded locales.
+
+**After optimization:**
+
+- Common case (`en-US`): **1.39ms** per instantiation
+- Chinese locales (`zh-TW`): **1.40ms** per instantiation
+- Serbo-Croatian locales: **1.38ms** per instantiation
+
+**Performance improvement: 439x faster** 🚀
+
+### Three-Tier Optimization
+
+The algorithm uses three tiers for maximum performance:
+
+1. **Tier 1 (Exact Match)**: O(1) Set lookup for exact locale matches
+2. **Tier 2 (Maximization + Fallback)**: Progressive subtag removal with locale maximization
+3. **Tier 3 (CLDR Distance)**: Full UTS #35 Enhanced Language Matching with memoization
+
+This design ensures that common cases (exact matches and simple fallbacks) are extremely fast, while complex scenarios (script/region matching, language distances) still perform well.

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Dependency changes

• + Added

  @formatjs/fast-memoize@3.0.1

• + Added

  @formatjs/fast-memoize@3.0.1
  (transitive)