From 04c9b3507e6bb6f1beb8b10c5ab32318a9a6b6e9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?G=C3=BCrg=C3=BCn=20Day=C4=B1o=C4=9Flu?= <hey@gurgun.day>
Date: Fri, 30 Aug 2024 12:32:21 +0200
Subject: [PATCH] perf: improve sparse escape (#27)

* improve escape

* escape

* improve escape

* add sparse escape

* improve branching

* start

* no unnecessary assignment

* use already created var
---
 bench/index.js |  4 +++
 src/html.js    | 90 ++++++++++++++++++++++++--------------------------
 2 files changed, 48 insertions(+), 46 deletions(-)

diff --git a/bench/index.js b/bench/index.js
index c7b7c61..d944dc2 100644
--- a/bench/index.js
+++ b/bench/index.js
@@ -104,6 +104,10 @@ bench.add("mixed escaped and unescaped expressions", () => {
   `;
 });
 
+bench.add("sparse escape", () => {
+  result = html`<p>${`${"noescape".repeat(250)}<>`.repeat(5)}</p>`;
+});
+
 await bench.warmup();
 await bench.run();
 
diff --git a/src/html.js b/src/html.js
index ec5b262..60584d0 100644
--- a/src/html.js
+++ b/src/html.js
@@ -1,41 +1,41 @@
-const escapeRegExp = /["&'<=>]/;
+const escapeRegExp = /["&'<=>]/g;
 
 const escapeFunction = (string) => {
+  if (!string || !escapeRegExp.test(string)) {
+    return string;
+  }
+
   let escaped = "";
   let start = 0;
 
-  for (let end = 0; end !== string.length; ++end) {
-    switch (string.charCodeAt(end)) {
+  do {
+    const i = escapeRegExp.lastIndex - 1;
+
+    switch (string.charCodeAt(i)) {
       case 34: // "
-        escaped += string.slice(start, end) + "&#34;";
-        start = end + 1;
-        continue;
+        escaped += string.slice(start, i) + "&#34;";
+        break;
       case 38: // &
-        escaped += string.slice(start, end) + "&#38;";
-        start = end + 1;
-        continue;
+        escaped += string.slice(start, i) + "&#38;";
+        break;
       case 39: // '
-        escaped += string.slice(start, end) + "&#39;";
-        start = end + 1;
-        continue;
+        escaped += string.slice(start, i) + "&#39;";
+        break;
       case 60: // <
-        escaped += string.slice(start, end) + "&#60;";
-        start = end + 1;
-        continue;
+        escaped += string.slice(start, i) + "&#60;";
+        break;
       case 61: // =
-        escaped += string.slice(start, end) + "&#61;";
-        start = end + 1;
-        continue;
+        escaped += string.slice(start, i) + "&#61;";
+        break;
       case 62: // >
-        escaped += string.slice(start, end) + "&#62;";
-        start = end + 1;
-        continue;
+        escaped += string.slice(start, i) + "&#62;";
+        break;
     }
-  }
 
-  escaped += string.slice(start);
+    start = escapeRegExp.lastIndex;
+  } while (escapeRegExp.test(string));
 
-  return escaped;
+  return escaped + string.slice(start);
 };
 
 /**
@@ -59,16 +59,14 @@ export const html = ({ raw: literals }, ...expressions) => {
 
     if (literal && literal.charCodeAt(literal.length - 1) === 33) {
       literal = literal.slice(0, -1);
-    } else if (string && escapeRegExp.test(string)) {
+    } else {
       string = escapeFunction(string);
     }
 
     accumulator += literal + string;
   }
 
-  accumulator += literals[expressions.length];
-
-  return accumulator;
+  return accumulator + literals[expressions.length];
 };
 
 /**
@@ -120,11 +118,11 @@ export const htmlGenerator = function* ({ raw: literals }, ...expressions) {
                   string = `${expression}`;
                 }
 
-                if (string) {
-                  if (!isRaw && escapeRegExp.test(string)) {
-                    string = escapeFunction(string);
-                  }
+                if (!isRaw) {
+                  string = escapeFunction(string);
+                }
 
+                if (string) {
                   yield string;
                 }
               }
@@ -135,11 +133,11 @@ export const htmlGenerator = function* ({ raw: literals }, ...expressions) {
             string = `${expression}`;
           }
 
-          if (string) {
-            if (!isRaw && escapeRegExp.test(string)) {
-              string = escapeFunction(string);
-            }
+          if (!isRaw) {
+            string = escapeFunction(string);
+          }
 
+          if (string) {
             yield string;
           }
         }
@@ -152,7 +150,7 @@ export const htmlGenerator = function* ({ raw: literals }, ...expressions) {
 
     if (literal && literal.charCodeAt(literal.length - 1) === 33) {
       literal = literal.slice(0, -1);
-    } else if (string && escapeRegExp.test(string)) {
+    } else {
       string = escapeFunction(string);
     }
 
@@ -221,11 +219,11 @@ export const htmlAsyncGenerator = async function* (
                   string = `${expression}`;
                 }
 
-                if (string) {
-                  if (!isRaw && escapeRegExp.test(string)) {
-                    string = escapeFunction(string);
-                  }
+                if (!isRaw) {
+                  string = escapeFunction(string);
+                }
 
+                if (string) {
                   yield string;
                 }
               }
@@ -236,11 +234,11 @@ export const htmlAsyncGenerator = async function* (
             string = `${expression}`;
           }
 
-          if (string) {
-            if (!isRaw && escapeRegExp.test(string)) {
-              string = escapeFunction(string);
-            }
+          if (!isRaw) {
+            string = escapeFunction(string);
+          }
 
+          if (string) {
             yield string;
           }
         }
@@ -253,7 +251,7 @@ export const htmlAsyncGenerator = async function* (
 
     if (literal && literal.charCodeAt(literal.length - 1) === 33) {
       literal = literal.slice(0, -1);
-    } else if (string && escapeRegExp.test(string)) {
+    } else {
       string = escapeFunction(string);
     }