diff --git a/src/@prototypes/index.ts b/src/@prototypes/index.ts
new file mode 100644
index 00000000..51bda67e
--- /dev/null
+++ b/src/@prototypes/index.ts
@@ -0,0 +1 @@
+import "./map";
diff --git a/src/@prototypes/map.ts b/src/@prototypes/map.ts
new file mode 100644
index 00000000..40d4d20d
--- /dev/null
+++ b/src/@prototypes/map.ts
@@ -0,0 +1,16 @@
+Map.prototype.getOrInsert ??= function (key, defaultValue) {
+  const value = this.get(key);
+  if (value !== undefined) return value;
+
+  this.set(key, defaultValue);
+  return defaultValue;
+};
+
+Map.prototype.getOrInsertComputed ??= function (key, callback) {
+  const value = this.get(key);
+  if (value !== undefined) return value;
+
+  const defaultValue = callback(key);
+  this.set(key, defaultValue);
+  return defaultValue;
+};
diff --git a/src/extension.ts b/src/extension.ts
index 271c2783..d7a4c672 100644
--- a/src/extension.ts
+++ b/src/extension.ts
@@ -1,4 +1,5 @@
 import type { ExtensionContext } from "vscode";
+import "./@prototypes";
 import ExtensionCore from "./core/extension";
 import { localize } from "./localize";