Add MIME type module

js/modules/types/mime.js

@@ -0,0 +1,3 @@
+exports.isJPEG = mimeType =>
+  mimeType === 'image/jpeg' ||
+  mimeType === 'image/jpg';

test/modules/types/mime_test.js

@@ -0,0 +1,23 @@
+const { assert } = require('chai');
+
+const MIME = require('../../../js/modules/types/mime');
+
+
+describe('MIME', () => {
+  describe('isJPEG', () => {
+    it('should return true for `image/jpeg`', () => {
+      assert.isTrue(MIME.isJPEG('image/jpeg'));
+    });
+
+    it('should return true for `image/jpg`', () => {
+      assert.isTrue(MIME.isJPEG('image/jpeg'));
+    });
+
+    ['image/gif', 'image/tiff', 'application/json', 0, false, null, undefined]
+      .forEach((value) => {
+        it(`should return false for \`${value}\``, () => {
+          assert.isFalse(MIME.isJPEG(value));
+        });
+      });
+  });
+});