buffer: remove obsolete NaN check

These two NaN entries are not necessary and we can safely remove them.

PR-URL: #18744
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

lib/buffer.js

@@ -378,10 +378,7 @@ function fromArrayBuffer(obj, byteOffset, length) {
   } else {
     // convert length to non-negative integer
     length = +length;
-    // Check for NaN
-    if (length !== length) {
-      length = 0;
-    } else if (length > 0) {
+    if (length > 0) {
       if (length > maxLength)
         throw new errors.RangeError('ERR_BUFFER_OUT_OF_BOUNDS', 'length');
     } else {
@@ -404,7 +401,7 @@ function fromObject(obj) {
   }
 
   if (obj.length !== undefined || isAnyArrayBuffer(obj.buffer)) {
-    if (typeof obj.length !== 'number' || obj.length !== obj.length) {
+    if (typeof obj.length !== 'number') {
       return new FastBuffer();
     }
     return fromArrayLike(obj);

test/parallel/test-buffer-arraybuffer.js

@@ -148,3 +148,6 @@ b.writeDoubleBE(11.11, 0, true);
     message: '"length" is outside of buffer bounds'
   });
 }
+
+// Test an array like entry with the length set to NaN.
+assert.deepStrictEqual(Buffer.from({ length: NaN }), Buffer.alloc(0));