Object.freeze特性
Object.freeze()是ES5新增的特性，可以冻结一个对象，冻结指的是不能向这个对象添加新的属性，不能修改其已有属性的值，不能删除已有属性，以及不能修改该对象已有属性的可枚举性、可配置性、可写性。防止对象被修改。 如果你有一个巨大的数组或Object，并且确信数据不会修改，使用Object.freeze()可以让性能大幅提升。
Object.freeze()接受一个对象作为参数，并返回一个相同的不可变的对象。这就意味着我们不能添加，删除或更改对象的任何属性
使用场景
对于纯展示的大数据，都可以使用Object.freeze提升性能
演示代码
const COMMANDS = Object.freeze({ EDIT_COPY: 'edit.copy', EDIT_COPY_AS_HTML: 'edit.copy-as-html', EDIT_COPY_AS_MARKDOWN: 'edit.copy-as-markdown', EDIT_CREATE_PARAGRAPH: 'edit.create-paragraph', EDIT_CUT: 'edit.cut', EDIT_DELETE_PARAGRAPH: 'edit.delete-paragraph', EDIT_DUPLICATE: 'edit.duplicate', EDIT_FIND: 'edit.find', EDIT_FIND_IN_FOLDER: 'edit.find-in-folder', EDIT_FIND_NEXT: 'edit.find-next', EDIT_FIND_PREVIOUS: 'edit.find-previous', EDIT_PASTE: 'edit.paste', EDIT_PASTE_AS_PLAINTEXT: 'edit.paste-as-plaintext', EDIT_REDO: 'edit.redo', EDIT_REPLACE: 'edit.replace', EDIT_SCREENSHOT: 'edit.screenshot', EDIT_SELECT_ALL: 'edit.select-all', EDIT_UNDO: 'edit.undo', FILE_CHECK_UPDATE: 'file.check-update', FILE_CLOSE_TAB: 'file.close-tab', FILE_CLOSE_WINDOW: 'file.close-window', FILE_EXPORT_FILE: 'file.export-file', FILE_IMPORT_FILE: 'file.import-file', FILE_MOVE_FILE: 'file.move-file', FILE_NEW_FILE: 'file.new-window', FILE_NEW_TAB: 'file.new-tab', FILE_OPEN_FILE: 'file.open-file', FILE_OPEN_FOLDER: 'file.open-folder', FILE_PREFERENCES: 'file.preferences', FILE_PRINT: 'file.print', FILE_QUICK_OPEN: 'file.quick-open', FILE_QUIT: 'file.quit', FILE_RENAME_FILE: 'file.rename-file', FILE_SAVE: 'file.save', FILE_SAVE_AS: 'file.save-as', // FILE_TOGGLE_AUTO_SAVE: 'file.toggle-auto-save', FORMAT_CLEAR_FORMAT: 'format.clear-format', FORMAT_EMPHASIS: 'format.emphasis', FORMAT_HIGHLIGHT: 'format.highlight', FORMAT_HYPERLINK: 'format.hyperlink', FORMAT_IMAGE: 'format.image', FORMAT_INLINE_CODE: 'format.inline-code', FORMAT_INLINE_MATH: 'format.inline-math', FORMAT_STRIKE: 'format.strike', FORMAT_STRONG: 'format.strong', FORMAT_SUBSCRIPT: 'format.subscript', FORMAT_SUPERSCRIPT: 'format.superscript', FORMAT_UNDERLINE: 'format.underline', MT_HIDE: 'mt.hide', MT_HIDE_OTHERS: 'mt.hide-others', PARAGRAPH_BULLET_LIST: 'paragraph.bullet-list', PARAGRAPH_CODE_FENCE: 'paragraph.code-fence', PARAGRAPH_DEGRADE_HEADING: 'paragraph.degrade-heading', PARAGRAPH_FRONT_MATTER: 'paragraph.front-matter', PARAGRAPH_HEADING_1: 'paragraph.heading-1', PARAGRAPH_HEADING_2: 'paragraph.heading-2', PARAGRAPH_HEADING_3: 'paragraph.heading-3', PARAGRAPH_HEADING_4: 'paragraph.heading-4', PARAGRAPH_HEADING_5: 'paragraph.heading-5', PARAGRAPH_HEADING_6: 'paragraph.heading-6', PARAGRAPH_HORIZONTAL_LINE: 'paragraph.horizontal-line', PARAGRAPH_HTML_BLOCK: 'paragraph.html-block', PARAGRAPH_LOOSE_LIST_ITEM: 'paragraph.loose-list-item', PARAGRAPH_MATH_FORMULA: 'paragraph.math-formula', PARAGRAPH_ORDERED_LIST: 'paragraph.order-list', PARAGRAPH_PARAGRAPH: 'paragraph.paragraph', PARAGRAPH_QUOTE_BLOCK: 'paragraph.quote-block', PARAGRAPH_TABLE: 'paragraph.table', PARAGRAPH_TASK_LIST: 'paragraph.task-list', PARAGRAPH_INCREASE_HEADING: 'paragraph.upgrade-heading', TABS_CYCLE_BACKWARD: 'tabs.cycle-backward', TABS_CYCLE_FORWARD: 'tabs.cycle-forward', TABS_SWITCH_TO_EIGHTH: 'tabs.switch-to-eighth', TABS_SWITCH_TO_FIFTH: 'tabs.switch-to-fifth', TABS_SWITCH_TO_FIRST: 'tabs.switch-to-first', TABS_SWITCH_TO_FOURTH: 'tabs.switch-to-fourth', TABS_SWITCH_TO_LEFT: 'tabs.switch-to-left', TABS_SWITCH_TO_NINTH: 'tabs.switch-to-ninth', TABS_SWITCH_TO_RIGHT: 'tabs.switch-to-right', TABS_SWITCH_TO_SECOND: 'tabs.switch-to-second', TABS_SWITCH_TO_SEVENTH: 'tabs.switch-to-seventh', TABS_SWITCH_TO_SIXTH: 'tabs.switch-to-sixth', TABS_SWITCH_TO_TENTH: 'tabs.switch-to-tenth', TABS_SWITCH_TO_THIRD: 'tabs.switch-to-third', VIEW_COMMAND_PALETTE: 'view.command-palette', VIEW_DEV_RELOAD: 'view.dev-reload', VIEW_FOCUS_MODE: 'view.focus-mode', VIEW_FORCE_RELOAD_IMAGES: 'view.reload-images', VIEW_SOURCE_CODE_MODE: 'view.source-code-mode', VIEW_TOGGLE_DEV_TOOLS: 'view.toggle-dev-tools', VIEW_TOGGLE_SIDEBAR: 'view.toggle-sidebar', VIEW_TOGGLE_TABBAR: 'view.toggle-tabbar', VIEW_TOGGLE_TOC: 'view.toggle-toc', VIEW_TYPEWRITER_MODE: 'view.typewriter-mode', WINDOW_MINIMIZE: 'window.minimize', WINDOW_TOGGLE_ALWAYS_ON_TOP: 'window.toggle-always-on-top', WINDOW_TOGGLE_FULL_SCREEN: 'window.toggle-full-screen', WINDOW_ZOOM_IN: 'window.zoom-in', WINDOW_ZOOM_OUT: 'window.zoom-out' }) export default COMMANDS