fix(node): return false from vm.isContext (#21568)

#20851 (comment)
for `jsdom`

Author: littledivy

cli/tests/unit_node/vm_test.ts

@@ -1,5 +1,5 @@
 // Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
-import { runInNewContext } from "node:vm";
+import { isContext, runInNewContext } from "node:vm";
 import {
   assertEquals,
   assertThrows,
@@ -55,3 +55,15 @@ Deno.test({
     }
   },
 });
+
+Deno.test({
+  name: "vm isContext",
+  fn() {
+    // Currently we do not expose VM contexts so this is always false.
+    const obj = {};
+    assertEquals(isContext(obj), false);
+    assertEquals(isContext(globalThis), false);
+    const sandbox = runInNewContext("{}");
+    assertEquals(isContext(sandbox), false);
+  },
+});

ext/node/polyfills/vm.ts

@@ -75,7 +75,8 @@ export function runInThisContext(
 }
 
 export function isContext(_maybeContext: any) {
-  notImplemented("isContext");
+  // TODO(@littledivy): Currently we do not expose contexts so this is always false.
+  return false;
 }
 
 export function compileFunction(_code: string, _params: any, _options: any) {