From abfb2321b6ce390a38ab3b927246e4175ad7e712 Mon Sep 17 00:00:00 2001
From: Craig Spence <craigspence0@gmail.com>
Date: Wed, 27 Feb 2019 18:03:17 +1300
Subject: [PATCH 1/2] Add memo cache to improve performance of repeated parse
 calls

---
 esquery.js      | 10 ++++++++--
 tests/parser.js |  9 +++++++--
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/esquery.js b/esquery.js
index 97407ff..f2de80e 100644
--- a/esquery.js
+++ b/esquery.js
@@ -1,6 +1,5 @@
 /* vim: set sw=4 sts=4 : */
 (function () {
-
     var estraverse = require('estraverse');
     var parser = require('./parser');
 
@@ -8,6 +7,8 @@
         return {}.toString.call(array) === '[object Array]';
     };
 
+    var PARSE_CACHE = {};
+
     var LEFT_SIDE = {};
     var RIGHT_SIDE = {};
 
@@ -312,7 +313,12 @@
          * Parse a selector string and return its AST.
          */
         function parse(selector) {
-            return parser.parse(selector);
+            if (PARSE_CACHE[selector]) {
+                return PARSE_CACHE[selector];
+            }
+            var parsed = parser.parse(selector);
+            PARSE_CACHE[selector] = parsed;
+            return parsed;
         }
 
         /**
diff --git a/tests/parser.js b/tests/parser.js
index d79f093..3247081 100644
--- a/tests/parser.js
+++ b/tests/parser.js
@@ -2,7 +2,8 @@ define([
     "esquery",
     "jstestr/assert",
     "jstestr/test",
-], function (esquery, assert, test) {
+    "perf_hooks"
+], function (esquery, assert, test, performance) {
 
     test.defineSuite("basic query parsing", {
 
@@ -18,7 +19,11 @@ define([
             assert.isNotEqual(void 0, esquery.parse("A     "));
             assert.isNotEqual(void 0, esquery.parse(" A "));
             assert.isNotEqual(void 0, esquery.parse("     A     "));
-        }
+        },
 
+        "memoize selector parsing": function () {
+            assert.isEqual(JSON.stringify(esquery.parse("A")) === JSON.stringify(esquery.parse("A")), true);
+            assert.isEqual(esquery.parse("A") === esquery.parse("A"), true);
+        }
     });
 });

From 7d95ac960e58d9cf5577eb953a07df187ce4708b Mon Sep 17 00:00:00 2001
From: Craig Spence <craigspence0@gmail.com>
Date: Wed, 27 Feb 2019 18:04:21 +1300
Subject: [PATCH 2/2] Remove leftover test code

---
 tests/parser.js | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tests/parser.js b/tests/parser.js
index 3247081..de58d2c 100644
--- a/tests/parser.js
+++ b/tests/parser.js
@@ -1,9 +1,8 @@
 define([
     "esquery",
     "jstestr/assert",
-    "jstestr/test",
-    "perf_hooks"
-], function (esquery, assert, test, performance) {
+    "jstestr/test"
+], function (esquery, assert, test) {
 
     test.defineSuite("basic query parsing", {