passim: replace instanceof with Buffer.isBuffer

instanceOf check may fail in browser environment where multiple
versions of the buffer package may be bundled together, hence
resulting in different instances of Buffer being present in the
code. A more resilient way of checking whether the parameter supplied
is a buffer is the Buffer.isBuffer() method which I'm migrating to in
this PR.

From #24.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Change Log
 
+## [1.2.1] - 2021-04-29
+
+* Improve [browser compatibility][pr#24] by using `Buffer.isBuffer` instead of
+  `instanceof` to confirm Buffer types.
+
 ## [1.2.0] - 2018-03-14
 
 * **API** Add [UTF8][doc:UTF8] to encode UTF strings in a possibly
@@ -131,6 +136,7 @@
 
 * Initial release.
 
+[1.2.1]: https://github.com/pabigot/buffer-layout/compare/v1.2.0...v1.2.1
 [1.2.0]: https://github.com/pabigot/buffer-layout/compare/v1.1.0...v1.2.0
 [1.1.0]: https://github.com/pabigot/buffer-layout/compare/v1.0.0...v1.1.0
 [1.0.0]: https://github.com/pabigot/buffer-layout/compare/v0.13.0...v1.0.0
@@ -193,6 +199,7 @@
 [issue#19]: https://github.com/pabigot/buffer-layout/issues/19
 [issue#20]: https://github.com/pabigot/buffer-layout/issues/20
 [issue#21]: https://github.com/pabigot/buffer-layout/issues/21
+[pr#24]: https://github.com/pabigot/buffer-layout/pull/24
 [ci:travis]: https://travis-ci.org/pabigot/buffer-layout
 [ci:coveralls]: https://coveralls.io/github/pabigot/buffer-layout
 [node:issue#3992]: https://github.com/nodejs/node/issues/3992

lib/Layout.js

@@ -1765,7 +1765,7 @@ class Union extends Layout {
    */
   getVariant(vb, offset) {
     let variant = vb;
-    if (vb instanceof Buffer) {
+    if (Buffer.isBuffer(vb)) {
       if (undefined === offset) {
         offset = 0;
       }
@@ -2325,7 +2325,7 @@ class Blob extends Layout {
     if (this.length instanceof ExternalLayout) {
       span = src.length;
     }
-    if (!((src instanceof Buffer)
+    if (!(Buffer.isBuffer(src)
           && (span === src.length))) {
       throw new TypeError(nameWithProperty('Blob.encode', this)
                           + ' requires (length ' + span + ') Buffer as src');
@@ -2361,7 +2361,7 @@ class CString extends Layout {
 
   /** @override */
   getSpan(b, offset) {
-    if (!(b instanceof Buffer)) {
+    if (!Buffer.isBuffer(b)) {
       throw new TypeError('b must be a Buffer');
     }
     if (undefined === offset) {
@@ -2452,7 +2452,7 @@ class UTF8 extends Layout {
 
   /** @override */
   getSpan(b, offset) {
-    if (!(b instanceof Buffer)) {
+    if (!Buffer.isBuffer(b)) {
       throw new TypeError('b must be a Buffer');
     }
     if (undefined === offset) {

package.json

@@ -1,6 +1,6 @@
 {
   "name": "buffer-layout",
-  "version": "1.2.0",
+  "version": "1.2.1",
   "description": "Translation between JavaScript values and Buffers",
   "keywords": [
     "Buffer",