diff --git a/perf.js b/perf.js
new file mode 100644
index 0000000..d468025
--- /dev/null
+++ b/perf.js
@@ -0,0 +1,15 @@
+console.clear();
+
+const n = 10 ** 8;
+// const map = new Map();
+
+console.log('sequential insertion');
+for(let run = 0; run < 10; run ++) {
+  const arr = [];
+
+  console.time('array');
+  for(let i = 0; i < n; i ++) {
+    arr.push(133769420)
+  }
+  console.timeEnd('array')
+}
\ No newline at end of file