convert macOS check to utility function

src/components/Editor.tsx

@@ -17,6 +17,7 @@ import { connect } from 'react-redux';
 import { Action, Dispatch } from '../actions';
 import { setEditSession, storageChanged } from '../actions/editor';
 import { RootState } from '../reducers';
+import { isMacOS } from '../utils/os';
 import { EditorStringId } from './editor-i18n';
 import en from './editor-i18n.en.json';
 
@@ -142,7 +143,7 @@ class Editor extends React.Component<EditorProps> {
                     }}
                     text={i18n.translate(EditorStringId.Copy)}
                     icon="duplicate"
-                    label={/mac/i.test(navigator.platform) ? 'Cmd-C' : 'Ctrl-C'}
+                    label={isMacOS() ? 'Cmd-C' : 'Ctrl-C'}
                     disabled={this.editor?.getSelection().isEmpty()}
                 />
                 <MenuItem
@@ -154,7 +155,7 @@ class Editor extends React.Component<EditorProps> {
                     }}
                     text={i18n.translate(EditorStringId.Paste)}
                     icon="clipboard"
-                    label={/mac/i.test(navigator.platform) ? 'Cmd-V' : 'Ctrl-V'}
+                    label={isMacOS() ? 'Cmd-V' : 'Ctrl-V'}
                 />
                 <MenuDivider />
                 <MenuItem

src/components/Terminal.tsx

@@ -17,6 +17,7 @@ import { FitAddon } from 'xterm-addon-fit';
 import { Dispatch } from '../actions';
 import { receiveData } from '../actions/terminal';
 import { RootState } from '../reducers';
+import { isMacOS } from '../utils/os';
 import { TerminalStringId } from './terminal-i18n';
 import en from './terminal-i18n.en.json';
 
@@ -137,7 +138,7 @@ class Terminal extends React.Component<TerminalProps> {
                     }}
                     text={i18n.translate(TerminalStringId.Copy)}
                     icon="duplicate"
-                    label={/mac/i.test(navigator.platform) ? 'Cmd-C' : 'Ctrl-Shift-C'}
+                    label={isMacOS() ? 'Cmd-C' : 'Ctrl-Shift-C'}
                     disabled={!this.xterm.hasSelection()}
                 />
                 <MenuItem
@@ -146,7 +147,7 @@ class Terminal extends React.Component<TerminalProps> {
                     }}
                     text={i18n.translate(TerminalStringId.Paste)}
                     icon="clipboard"
-                    label={/mac/i.test(navigator.platform) ? 'Cmd-V' : 'Ctrl-V'}
+                    label={isMacOS() ? 'Cmd-V' : 'Ctrl-V'}
                 />
                 <MenuDivider />
                 <MenuItem

src/utils/os.test.ts

@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2021 The Pybricks Authors
+
+import { isMacOS } from './os';
+
+describe('isMacOS', () => {
+    test('is true', () => {
+        jest.spyOn(navigator, 'platform', 'get').mockReturnValue('MacIntel');
+        expect(isMacOS()).toBeTruthy();
+    });
+    test('is false', () => {
+        jest.spyOn(navigator, 'platform', 'get').mockReturnValue('Win32');
+        expect(isMacOS()).toBeFalsy();
+    });
+});

src/utils/os.ts

@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2021 The Pybricks Authors
+
+// Utility functions for dealing with operating systems.
+
+export function isMacOS(): boolean {
+    return /mac/i.test(navigator.platform);
+}