util: create hex style cache and fast path

Author: araujogui

lib/util.js

@@ -114,7 +114,11 @@ const kEscapeEnd = 'm';
 const kDimCode = 2;
 const kBoldCode = 1;
 
+// Close sequence for 24-bit foreground colors (reset to default foreground)
+const kHexCloseSeq = kEscape + '39' + kEscapeEnd;
+
 let styleCache;
+const hexStyleCache = { __proto__: null };
 
 function getStyleCache() {
   if (styleCache === undefined) {
@@ -137,6 +141,25 @@ function getStyleCache() {
   return styleCache;
 }
 
+/**
+ * Returns the cached ANSI escape sequences for a hex color.
+ * Computes and caches on first use to avoid repeated Buffer allocations.
+ * @param {string} hex A valid hex color string (#RGB or #RRGGBB)
+ * @returns {{openSeq: string, closeSeq: string}}
+ */
+function getHexStyle(hex) {
+  const cached = hexStyleCache[hex];
+  if (cached !== undefined) return cached;
+  const { 0: r, 1: g, 2: b } = hexToRgb(hex);
+  const style = {
+    __proto__: null,
+    openSeq: kEscape + rgbToAnsi24Bit(r, g, b) + kEscapeEnd,
+    closeSeq: kHexCloseSeq,
+  };
+  hexStyleCache[hex] = style;
+  return style;
+}
+
 function replaceCloseCode(str, closeSeq, openSeq, keepClose) {
   const closeLen = closeSeq.length;
   let index = str.indexOf(closeSeq);
@@ -163,15 +186,6 @@ function replaceCloseCode(str, closeSeq, openSeq, keepClose) {
 // Matches #RGB or #RRGGBB
 const hexColorRegExp = /^#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6})$/;
 
-/**
- * Validates whether a string is a valid hex color code.
- * @param {string} hex The hex string to validate (e.g., '#fff' or '#ffffff')
- * @returns {boolean} True if valid hex color, false otherwise
- */
-function isValidHexColor(hex) {
-  return typeof hex === 'string' && RegExpPrototypeExec(hexColorRegExp, hex) !== null;
-}
-
 /**
  * Parses a hex color string into RGB components.
  * Supports both 3-digit (#RGB) and 6-digit (#RRGGBB) formats.
@@ -225,6 +239,17 @@ function styleText(format, text, options) {
       const processed = replaceCloseCode(text, style.closeSeq, style.openSeq, style.keepClose);
       return style.openSeq + processed + style.closeSeq;
     }
+
+    if (format[0] === '#') {
+      let hexStyle = hexStyleCache[format];
+      if (hexStyle === undefined && RegExpPrototypeExec(hexColorRegExp, format) !== null) {
+        hexStyle = getHexStyle(format);
+      }
+      if (hexStyle !== undefined) {
+        const processed = replaceCloseCode(text, hexStyle.closeSeq, hexStyle.openSeq, false);
+        return hexStyle.openSeq + processed + hexStyle.closeSeq;
+      }
+    }
   }
 
   validateString(text, 'text');
@@ -255,24 +280,24 @@ function styleText(format, text, options) {
   for (const key of formatArray) {
     if (key === 'none') continue;
 
-    if (isValidHexColor(key)) {
+    if (typeof key === 'string' && key[0] === '#') {
+      let hexStyle = hexStyleCache[key];
+      if (hexStyle === undefined) {
+        if (RegExpPrototypeExec(hexColorRegExp, key) === null) {
+          throw new ERR_INVALID_ARG_VALUE('format', key,
+                                          'must be a valid hex color (#RGB or #RRGGBB)');
+        }
+        hexStyle = getHexStyle(key);
+      }
       if (skipColorize) continue;
-      const { 0: r, 1: g, 2: b } = hexToRgb(key);
-      const openSeq = kEscape + rgbToAnsi24Bit(r, g, b) + kEscapeEnd;
-      const closeSeq = kEscape + '39' + kEscapeEnd;
-      openCodes += openSeq;
-      closeCodes = closeSeq + closeCodes;
-      processedText = replaceCloseCode(processedText, closeSeq, openSeq, false);
+      openCodes += hexStyle.openSeq;
+      closeCodes = hexStyle.closeSeq + closeCodes;
+      processedText = replaceCloseCode(processedText, hexStyle.closeSeq, hexStyle.openSeq, false);
       continue;
     }
 
     const style = cache[key];
     if (style === undefined) {
-      // Check if it looks like an invalid hex color (starts with #)
-      if (typeof key === 'string' && key[0] === '#') {
-        throw new ERR_INVALID_ARG_VALUE('format', key,
-                                        'must be a valid hex color (#RGB or #RRGGBB)');
-      }
       validateOneOf(key, 'format', ObjectGetOwnPropertyNames(inspect.colors));
     }
     openCodes += style.openSeq;