The scope of JavaScript determines the accessibility scope of variables, which are divided into global, function and block-level scope; the context determines the direction of this and depends on the function call method. 1. Scopes include global scope (accessible anywhere), function scope (only valid within the function), and block-level scope (let and const are valid within {}). 2. The execution context contains the variable object, scope chain and the values of this. This points to global or undefined in the ordinary function, the method call points to the call object, the constructor points to the new object, and can also be explicitly specified by call/apply/bind. 3. Closure refers to functions accessing and remembering external scope variables. They are often used for encapsulation and cache, but may cause

CompositionAPI in Vue3 is more suitable for complex logic and type derivation, and OptionsAPI is suitable for simple scenarios and beginners; 1. OptionsAPI organizes code according to options such as data and methods, and has clear structure but complex components are fragmented; 2. CompositionAPI uses setup to concentrate related logic, which is conducive to maintenance and reuse; 3. CompositionAPI realizes conflict-free and parameterizable logical reuse through composable functions, which is better than mixin; 4. CompositionAPI has better support for TypeScript and more accurate type derivation; 5. There is no significant difference in the performance and packaging volume of the two; 6.

There are two core methods to get the selected radio button value. 1. Use querySelector to directly obtain the selected item, and use the input[name="your-radio-name"]:checked selector to obtain the selected element and read its value attribute. It is suitable for modern browsers and has concise code; 2. Use document.getElementsByName to traverse and find the first checked radio through loop NodeList and get its value, which is suitable for scenarios that are compatible with old browsers or require manual control of the process; in addition, you need to pay attention to the spelling of the name attribute, handling unselected situations, and dynamic loading of content

There is an essential difference between JavaScript's WebWorkers and JavaThreads in concurrent processing. 1. JavaScript adopts a single-thread model. WebWorkers is an independent thread provided by the browser. It is suitable for performing time-consuming tasks that do not block the UI, but cannot operate the DOM; 2. Java supports real multithreading from the language level, created through the Thread class, suitable for complex concurrent logic and server-side processing; 3. WebWorkers use postMessage() to communicate with the main thread, which is highly secure and isolated; Java threads can share memory, so synchronization issues need to be paid attention to; 4. WebWorkers are more suitable for front-end parallel computing, such as image processing, and

Debugging complex JavaScript applications requires systematic use tools. 1. Set breakpoints and conditional breakpoints to intercept suspicious processes, such as before function entry, loop, asynchronous callback and filter according to conditions; 2. Enable Blackboxing function to block third-party library interference; 3. Use debugger statements to control debug entry based on environmental judgment; 4. Trace the call link through CallStack, analyze the execution path and variable status, thereby efficiently locate the root cause of the problem.

Type casting is the behavior of automatically converting one type of value to another type in JavaScript. Common scenarios include: 1. When using operators, if one side is a string, the other side will also be converted to a string, such as '5' 5. The result is "55"; 2. In the Boolean context, non-Boolean values will be implicitly converted to Boolean types, such as empty strings, 0, null, undefined, etc., which are considered false; 3. Null participates in numerical operations and will be converted to 0, and undefined will be converted to NaN; 4. The problems caused by implicit conversion can be avoided through explicit conversion functions such as Number(), String(), and Boolean(). Mastering these rules helps

Format dates in JavaScript can be implemented through native methods or third-party libraries. 1. Use native Date object stitching: Get the date part through getFullYear, getMonth, getDate and other methods, and manually splice it into YYYY-MM-DD and other formats, which is suitable for lightweight needs and does not rely on third-party libraries; 2. Use toLocaleDateString method: You can output such as MM/DD/YYYY format according to local habits, support multilingual, but the format may be inconsistent due to different environments; 3. Use third-party libraries such as day.js or date-fns: Provides concise syntax and rich functions, suitable for frequent operations or when extensibility is required, such as dayjs()

Initialize the project and create package.json; 2. Create an entry script index.js with shebang; 3. Register commands through bin fields in package.json; 4. Use yargs and other libraries to parse command line parameters; 5. Use npmlink local test; 6. Add help, version and options to enhance the experience; 7. Optionally publish through npmpublish; 8. Optionally achieve automatic completion with yargs; finally create practical CLI tools through reasonable structure and user experience design, complete automation tasks or distribute widgets, and end with complete sentences.