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A List in Dart is a built-in data structure representing an ordered collection of elements. Key characteristics include:
List.filled, which have a fixed length and cannot be expanded.The effect serves as the bridge between reactive data and side-effect functions. The lifecycle follows these steps:
get trap), the current effect is added to the dependency list for that property.set trap), the trigger function is called, which identifies and re-executes all associated effect functions.watch and watchEffect, or automatically when using reactive objects within a template.Set is a collection of unique elements. Duplicate elements are automatically ignored. Unlike a List, elements in a Set do not have a fixed order.Server-Sent Events (SSE) is a web technology that allows servers to push data to clients over a single HTTP connection.
Key Characteristics:
HTTP caching stores copies of Web resources (CSS, JS, images, pages) in the client (browser) or proxy servers (CDN) to reduce network resource usage, improve page performance, and lower server load.
Cache Priority Order:
Pragma > Cache-Control > Expires (Strong Cache) > Negotiated Cache (Weak Cache).
Key Header Definitions:
no-cache is used in request headers; behaves similarly to Cache-Control: no-cache.Last-Modified (response header) indicates the last modification time; If-Modified-Since (request header) is used for validation.ETag (response header) is a unique identifier/hash of the resource; If-None-Match (request header) is used for validation.private: Only the browser (private cache) can store the response.public: Both browser and proxy servers (shared cache) can store the response.max-age=seconds: Resource is considered fresh for N seconds after generation.s-maxage: Similar to max-age but specifically for shared caches.no-cache: Response can be stored but must be re-validated with the server before reuse.no-store: No part of the response may be cached; disables both strong and negotiated caching.no-transform: Proxies must not modify the media type.Service Workers run as independent threads in the browser background, allowing developers to intercept network requests and control page caching. This enables features like offline access, faster page loads, and push notifications. Unlike standard browser caching (strong/negotiation caching) which is managed by the browser via HTTP headers, Service Worker caching is manually controlled by the developer, providing finer granularity over storage time and update strategies.
Requirement: Service Workers must be deployed over HTTPS for security.
Dart provides three primary types for representing numbers:
int: Represents integer values.double: Represents floating-point numbers.num: A supertype that can represent both integers and floating-point numbers.Proxy object to intercept basic operations (like property lookup, assignment, and deletion) on objects, replacing the Object.defineProperty approach used in Vue 2. Reflect is used to perform the actual operation on the target object. The primary advantage of Reflect is that it returns a boolean indicating success or failure instead of throwing errors, making the interception logic more robust.const obj = { name: 'Vue', age: 3 };
const proxyObj = new Proxy(obj, {
get(target, key, receiver) {
console.log(`getting ${key}`);
return Reflect.get(target, key, receiver);
},
set(target, key, value, receiver) {
console.log(`setting ${key} to ${value}`);
return Reflect.set(target, key, value, receiver);
},
deleteProperty(target, key) {
console.log(`deleting ${key}`);
return Reflect.deleteProperty(target, key);
},
ownKeys(target) {
return Reflect.ownKeys(target);
},
has(target, key) {
return Reflect.has(target, key);
},
});List<Object> mixedList = [1, 'two', 3.0, 'four', 5];
print(mixedList.length); // 5: Total number of elements
print(mixedList.first); // 1: First element
print(mixedList[0]); // 1: First element via index
print(mixedList.last); // 5: Last element
print(mixedList.isEmpty); // false: True if list is empty
print(mixedList.isNotEmpty); // true: True if list contains elements
print(mixedList.firstOrNull); // 1: First element, or null if list is emptyA basic multi-user chat system can be structured as follows:
Backend Stack:
ws: For WebSocket protocol implementation.express: For server framework.http: For handling the underlying HTTP server.Frontend Stack:
Vue 3: For reactive UI components.antdv: For UI components (Modals, Buttons).The backend (implemented with Express, Busboy, and fs) must provide three primary capabilities:
fs.statSync method in Node.js allows you to retrieve system information about a file, such as its modification time and size, which is useful for implementing Last-Modified headers.const fs = require('fs');
const stats = fs.statSync(path);
// Useful properties/methods:
console.log(stats.isFile()); // true if it's a file
console.log(stats.size); // File size in bytes