Information about the screen object

The `screen` object in JavaScript provides key information about the user's screen, including properties such as width, height, available space, and color depth. This information is crucial for responsive design and device adaptation. Developers can leverage these properties to adjust layouts or load resources of different resolutions based on varying screen sizes. Modern browsers also support extended properties like screen orientation and multi-monitor position detection. The article further covers methods for handling screen orientation changes, applications in multi-screen environments, and performance optimization tips such as caching results and using CSS media queries as an alternative to certain detection methods. Lastly, it mentions browser compatibility issues and advanced use cases like full-screen image galleries.

navigator object properties

The `navigator` object is a global object provided by the browser to retrieve browser-related information, containing numerous properties and methods for detecting browser type, version, operating system, etc. - `navigator.userAgent` returns the user agent string, which can determine the browser type and operating system. - `navigator.platform` returns the operating system platform. - `navigator.language` returns the browser's preferred language setting. - `navigator.cookieEnabled` indicates whether cookies are enabled. - `navigator.onLine` detects network status. - `navigator.geolocation` retrieves geographic location (requires user permission). - `navigator.clipboard` provides clipboard operations (must be used in a secure context). - `navigator.mediaDevices` accesses media devices like cameras and microphones. - `navigator.hardwareConcurrency` returns the number of processor cores. - `navigator.storage` queries storage space. - `navigator.deviceMemory` returns the device's memory size. - `navigator.vendor` returns browser vendor information. - `navigator.doNotTrack` detects the user's "Do Not Track" setting. - `navigator.connection` provides network connection information. - `navigator.permissions` queries permission status. - `navigator.getBattery` retrieves battery status. - `navigator.plugins` returns installed plugins. - `navigator.mimeTypes` returns supported MIME types. - `navigator.javaEnabled` checks if Java is enabled. - `navigator.sendBeacon` asynchronously sends small amounts of data, suitable for use during page unloading.

Event monitoring mode

The event listener pattern is the core mechanism for handling user interactions in JavaScript. Using the `addEventListener` method, event handlers can be registered. Event propagation consists of three phases: capture, target, and bubbling. Event delegation leverages the bubbling mechanism to handle child element events on a parent element. Custom events can be created and triggered. Asynchronous event handling uses `AbortController` to enable cancellable listeners. Performance optimization techniques include debouncing and throttling. Cross-browser compatibility requires consideration of legacy IE differences. The event object contains rich information such as coordinates and the triggering element. Modern frameworks like React and Vue encapsulate native events. Mobile support includes touch gesture events. Keyboard events enable precise input control. HTML5 provides native drag-and-drop functionality. Page lifecycle events monitor loading and unloading states. Network events detect connection changes. Media queries enable responsive design.

Asynchronous flow control

JavaScript asynchronous flow control is the core mechanism for handling non-blocking operations in a single-threaded language. Early implementations used callback functions but often led to callback hell, making code difficult to maintain. Promises provided a more elegant chaining solution. The ES2017 introduction of async/await syntax allowed asynchronous code to be written with synchronous-like readability. Parallel control can be achieved using Promise.all to execute multiple asynchronous operations simultaneously. Advanced scenarios requiring strategies like throttling or retries can leverage libraries like async.js or custom implementations. The event-driven pattern is suitable for handling multiple asynchronous events. Generator functions combined with Promises can achieve coroutine-like effects. Error handling requires global catching and middleware interception. Performance optimization must consider concurrency control and batch processing. These techniques are widely used in web development, including API calls, database operations, and file processing scenarios.

Asynchronous error handling

JavaScript asynchronous error handling faces numerous challenges, including the distinct mechanisms of callbacks, Promises, and async/await. Uncaught errors may lead to silent failures. Callbacks use the error-first pattern, with common issues such as forgetting to check error parameters and callback hell. Promises capture errors via the `catch` method, and unhandled rejections generate warnings. Async/await requires `try-catch` for error handling, while global error handlers can catch uncaught exceptions. Custom error types enable precise handling. In production, errors should be logged to monitoring systems. Testing asynchronous errors requires validating throws and handling. Performance considerations call for optimizing hot-path error handling. Differences exist between browser and Node.js environments, and third-party libraries follow their own conventions. Error recovery strategies, such as retry mechanisms, can be employed. Large-scale applications may design a centralized error-handling architecture.