From 6a2b86753b567c3056855ad115ccfba66064269b Mon Sep 17 00:00:00 2001
From: David Anson <david@dlaa.me>
Date: Sat, 2 Sep 2023 21:30:43 -0700
Subject: [PATCH] Reimplement micromark helper filterByPredicate to do fewer
 array manipulations for a ~6-7% elapsed time reduction.

---
 demo/markdownlint-browser.js | 32 +++++++++++++++++++++++---------
 helpers/micromark.cjs        | 35 ++++++++++++++++++++++++++---------
 2 files changed, 49 insertions(+), 18 deletions(-)

diff --git a/demo/markdownlint-browser.js b/demo/markdownlint-browser.js
index c1dd3656..6fc8f86e 100644
--- a/demo/markdownlint-browser.js
+++ b/demo/markdownlint-browser.js
@@ -1320,15 +1320,29 @@ function micromarkParse(markdown) {
  */
 function filterByPredicate(tokens, allowed, transformChildren) {
   var result = [];
-  var pending = _toConsumableArray(tokens);
-  var token = null;
-  while (token = pending.shift()) {
-    if (allowed(token)) {
-      result.push(token);
-    }
-    if (token.children.length > 0) {
-      var transformed = transformChildren ? transformChildren(token) : token.children;
-      pending.unshift.apply(pending, _toConsumableArray(transformed));
+  var queue = [{
+    "array": tokens,
+    "index": 0
+  }];
+  while (queue.length > 0) {
+    var current = queue[queue.length - 1];
+    var array = current.array,
+      index = current.index;
+    if (index < array.length) {
+      var token = array[current.index++];
+      if (allowed(token)) {
+        result.push(token);
+      }
+      var children = token.children;
+      if (children.length > 0) {
+        var transformed = transformChildren ? transformChildren(token) : children;
+        queue.push({
+          "array": transformed,
+          "index": 0
+        });
+      }
+    } else {
+      queue.pop();
     }
   }
   return result;
diff --git a/helpers/micromark.cjs b/helpers/micromark.cjs
index 5af8165b..fcc52e34 100644
--- a/helpers/micromark.cjs
+++ b/helpers/micromark.cjs
@@ -213,16 +213,33 @@ function micromarkParse(
  */
 function filterByPredicate(tokens, allowed, transformChildren) {
   const result = [];
-  const pending = [ ...tokens ];
-  let token = null;
-  while ((token = pending.shift())) {
-    if (allowed(token)) {
-      result.push(token);
+  const queue = [
+    {
+      "array": tokens,
+      "index": 0
     }
-    if (token.children.length > 0) {
-      const transformed =
-        transformChildren ? transformChildren(token) : token.children;
-      pending.unshift(...transformed);
+  ];
+  while (queue.length > 0) {
+    const current = queue[queue.length - 1];
+    const { array, index } = current;
+    if (index < array.length) {
+      const token = array[current.index++];
+      if (allowed(token)) {
+        result.push(token);
+      }
+      const { children } = token;
+      if (children.length > 0) {
+        const transformed =
+          transformChildren ? transformChildren(token) : children;
+        queue.push(
+          {
+            "array": transformed,
+            "index": 0
+          }
+        );
+      }
+    } else {
+      queue.pop();
     }
   }
   return result;