doc: correct getting an ArrayBuffer's length

`ArrayBuffer` instances do not have `.length` property.
Instead they have `.byteLength` property.
Fixed that in the description of
`new Buffer(arrayBuffer[, byteOffset[, length]])` and
`Buffer.from(arrayBuffer[, byteOffset[, length]])`.

PR-URL: #31632
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Yongsheng Zhang <[email protected]>
Reviewed-By: Gus Caplan <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>

doc/api/buffer.md

@@ -384,7 +384,7 @@ changes:
   [`SharedArrayBuffer`][] or the `.buffer` property of a [`TypedArray`][].
 * `byteOffset` {integer} Index of first byte to expose. **Default:** `0`.
 * `length` {integer} Number of bytes to expose.
-  **Default:** `arrayBuffer.length - byteOffset`.
+  **Default:** `arrayBuffer.byteLength - byteOffset`.
 
 This creates a view of the [`ArrayBuffer`][] or [`SharedArrayBuffer`][] without
 copying the underlying memory. For example, when passed a reference to the
@@ -830,7 +830,7 @@ added: v5.10.0
   [`SharedArrayBuffer`][], or the `.buffer` property of a [`TypedArray`][].
 * `byteOffset` {integer} Index of first byte to expose. **Default:** `0`.
 * `length` {integer} Number of bytes to expose.
-  **Default:** `arrayBuffer.length - byteOffset`.
+  **Default:** `arrayBuffer.byteLength - byteOffset`.
 
 This creates a view of the [`ArrayBuffer`][] without copying the underlying
 memory. For example, when passed a reference to the `.buffer` property of a