website·Indexed 32 days ago
https://elvinn.wiki/A personal technical wiki covering frontend development (React, Vue, TypeScript), backend common situations (locking mechanisms, log rotation), networking (HTTPS, CDN), and programming languages like C++ and Node.js. It also includes LeetCode problem-solving techniques, personal project documentation, and annual reading notes from 2020 to 2026.
MySQL utilizes several types of server logs to track different aspects of database operation:
long_query_time threshold.AsyncLocalStorage allows you to store data in a web request or any asynchronous process so that it can be accessed by subsequent sub-processes (including nested callbacks and async functions) without explicitly passing the data as arguments. It provides a way to achieve local-storage-like behavior within an asynchronous execution context.
Compatibility:
class Test {
int * arr{nullptr};
public:
Test():arr(new int[5000]{1,2,3,4}) {}
// Copy constructor: performs expensive deep copy
Test(const Test & t) {
if (arr == nullptr) arr = new int[5000];
memcpy(arr, t.arr, 5000*sizeof(int));
}
~Test(){ delete [] arr; }
};
Test createTest() {
return Test(); // Potential for multiple copy constructor calls
}Introduced in React 16.8, Hooks provide several architectural benefits but introduce new complexities for developers.
Advantages:
componentDidMount, componentDidUpdate, and componentWillUnmount.Disadvantages and Caveats:
Core Principle: The underlying mechanism of Hooks is based on arrays rather than magic.
Node.js uses the V8 engine, which manages memory via a Resident Set divided into Stack and Heap.
Stack: Managed by the OS; stores primitive data types and function call frames. Heap: Managed by V8; consists of several spaces:
Scavenge (Minor GC) algorithm.Mark-Sweep & Mark-Compact (Major GC). Divided into Pointer space (objects with pointers) and Data space (objects without pointers, e.g., strings).Page::kMaxRegularHeapObjectSize); these are not moved during GC.Tree Shaking is an optimization technique that removes unused code (dead code) from JavaScript bundles using static analysis. It works by parsing code into an Abstract Syntax Tree (AST), building a dependency graph from the entry point, marking unused code, and removing it.
Critical Requirement: Tree Shaking requires ES6 module syntax (import/export). It does not support CommonJS (CJS) because CJS modules are dynamic and dependencies are resolved at runtime, making static analysis impossible.
pnpm (performant node package manager) is a drop-in replacement for npm that optimizes dependency management using a centralized store and symlinks/hard links. It addresses three primary issues found in npm's flattened node_modules structure:
package.json. pnpm prevents this by using a non-flat directory structure, ensuring only explicitly declared dependencies in package.json are accessible to the application code.Hot Module Replacement (HMR) allows developers to update, add, or remove modules in a running application without a full page refresh, preserving the application state. The process generally follows these steps: