Add nullish values checking in Symbol.hasInstance (#82)

* Add nullish values checking in Symbol.hasInstance
* Fix for a test description
* Add an extension.
* Disable unicorn/import-index rule.
* Fix a typo

from.js

@@ -1,7 +1,9 @@
 const {statSync, createReadStream} = require('fs');
-const Blob = require('./index.js');
 const DOMException = require('domexception');
 
+// eslint-disable-next-line unicorn/import-index
+const Blob = require('./index.js');
+
 /**
  * @param {string} path filepath on the disk
  * @returns {Blob}
@@ -27,7 +29,7 @@ class BlobDataItem {
 		this.mtime = options.mtime;
 	}
 
-	// Slicing arguments is first validated and formated 
+	// Slicing arguments is first validated and formated
 	// to not be out of range by Blob.prototype.slice
 	slice(start, end) {
 		return new BlobDataItem({

index.js

@@ -160,6 +160,7 @@ class Blob {
 
 	static [Symbol.hasInstance](object) {
 		return (
+			object &&
 			typeof object === 'object' &&
 			typeof object.stream === 'function' &&
 			object.stream.length === 0 &&

test.js

@@ -160,3 +160,19 @@ test('Reading after modified should fail', async t => {
 	const error = await blob.text().catch(error => error);
 	t.is(error.name, 'NotReadableError');
 });
+
+test('Blob-ish class is an instance of Blob', t => {
+	class File {
+		stream() { }
+
+		get [Symbol.toStringTag]() {
+			return 'File';
+		}
+	}
+
+	t.true(new File() instanceof Blob);
+});
+
+test('Instanceof check returns false for nullish values', t => {
+	t.false(null instanceof Blob);
+});