net: add net.BlockList.isBlockList(value)

Author: jasnell

doc/api/net.md

@@ -170,6 +170,15 @@ added:
 
 The list of rules added to the blocklist.
 
+### `BlockList.isBlockList(value)`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `value` {any} Any JS value
+* Returns `true` if the `value` is a `net.BlockList`.
+
 ## Class: `net.SocketAddress`
 
 <!-- YAML

lib/internal/blocklist.js

@@ -43,6 +43,15 @@ class BlockList {
     this[kHandle][owner_symbol] = this;
   }
 
+  /**
+   * Returns true if the value is a BlockList
+   * @param {any} value
+   * @returns {boolean}
+   */
+  static isBlockList(value) {
+    return value?.[kHandle] !== undefined;
+  }
+
   [kInspect](depth, options) {
     if (depth < 0)
       return this;

test/parallel/test-blocklist.js

@@ -282,3 +282,8 @@ const util = require('util');
   assert(!blocklist.check('1.1.1.2'));
   assert(!blocklist.check('2.3.4.5'));
 }
+
+{
+  assert(BlockList.isBlockList(new BlockList()));
+  assert(!BlockList.isBlockList({}));
+}