主题： javascript

• 浏览器存储：比较 cookie、Web Storage 与 IndexedDB

  Cookie 会随每个请求传输，规范要求的容量较小；localStorage 和 sessionStorage 是同步字符串存储，每个源只有数 MiB；IndexedDB 是异步、支持事务的存储，共享源的较大配额。除非获准持久化，否则浏览器存储都是尽力保留，并按源划分。

  article · zh · reviewed · 知识截至 2026-09-15

• Using fetch with timeouts and AbortController

  A fetch promise rejects only on network failure, not on HTTP error status, and it has no timeout by itself. Pass an AbortSignal combined from AbortSignal.timeout and a caller's controller, check response.ok, and tell TimeoutError, AbortError, network errors and HTTP errors apart in the catch.

  methodology · en · reviewed · 知识截至 2026-09-15

• ES module builds with declared side effects shrink consumer bundles more than CommonJS builds

  Hypothesis: for a library of many independent functions, a consumer that imports a few of them gets a smaller bundle when the library ships ES modules with a sideEffects declaration than when it ships CommonJS, because tree shaking depends on static import/export structure; a fixture-based comparison is proposed.

  hypothesis · en · reviewed · 知识截至 2026-09-15

• Web Components：自定义元素、Shadow DOM 与封装的边界

  自定义元素用带连字符的标签名注册类，并提供生命周期回调；Shadow DOM 给予它作用域受限的子树，样式不会向任一方向泄漏；模板和声明式影子根提供标记。所有跨边界交互，从通过 parts 和自定义属性设置样式，到通过 ElementInternals 参与表单及关联标签，都必须有意开放。

  article · zh · reviewed · 知识截至 2026-09-16

• When does client-side routing still pay off now that browsers offer bfcache, prerendering and cross-document view transitions?

  Open question: in-page routers were adopted to avoid full page loads, at the cost of shell serving, 404 handling, scroll and focus restoration and a bundle that must arrive first; the back/forward cache, the Speculation Rules API and cross-document view transitions now address the original motivations in multi-page sites. For which sites and interaction patterns does an in-page router still measurably win?

  question · en · reviewed · 知识截至 2026-09-16

• 适应语言区域的界面：Intl 复数规则、日期与从右向左布局

  使用浏览器的 Intl 对象格式化数字、日期和相对时间，而不是手工操作字符串；按 Intl.PluralRules 类别选择复数形式，而不是判断 n == 1；使用 CSS 逻辑属性布局，让 dir=rtl 文档自行镜像，并为翻译后变长的文本留出空间。

  methodology · zh · reviewed · 知识截至 2026-09-16

• Node.js 中的 ES 模块与 CommonJS

  CommonJS 使用同步的 require 和 module.exports；ES 模块使用静态 import/export、顶层 await 和 import.meta。Node 根据文件扩展名以及最近的 package.json 中的 type 字段逐个判断模块类型。ES 模块要求完整文件扩展名，且没有 __dirname 和 require，但有文档说明的替代方式。

  article · zh · reviewed · 知识截至 2026-09-15

• JavaScript 文本偏移：区分 UTF-16 码元、码点和可见字符

  在每个编辑器或 API 边界处注明偏移量的单位，并在切分文本前有意识地进行转换。

  article · zh · reviewed · 知识截至 2026-09-22

• Rolling out a service worker safely: scope, versioned caches, the waiting worker and a kill switch

  A service worker that caches HTML can pin users to old code after a deploy. Register it with an explicit scope, fetch the script fresh on every update check, version caches per build and delete old ones on activate, choose per-resource strategies, decide how the waiting worker takes over, and ship a tested kill switch before the first release.

  methodology · en · reviewed · 知识截至 2026-09-16

• Keyboard navigation in composite widgets: roving tabindex, arrow keys and Escape

  Tab and Shift+Tab move between components; arrow keys move inside a component such as a tab list, toolbar, menu or radio group. Implement this with a roving tabindex (one item at tabindex=0, the rest at -1) or aria-activedescendant, close transient surfaces with Escape, and never trap focus without an advertised way out.

  article · en · reviewed · 知识截至 2026-09-16

• Focus management in single-page interactions: dialogs, route changes and removed elements

  When a page changes without a full load, keyboard focus must be moved on purpose: into a dialog when it opens and back to its trigger when it closes, to the new view's heading after a client-side route change, and to a sensible neighbour when the focused element is deleted. Otherwise focus falls to the document body and screen-reader users are sent back to the top.

  methodology · en · reviewed · 知识截至 2026-09-16

• 处理 Promise 与 async/await 中的错误

  async 函数会把 throw 转为 Promise 拒绝，await 则会重新抛出该错误；每个拒绝都必须有人负责处理。只包装能够恢复的操作，绝不放任 Promise 无人接管，允许部分失败时使用 allSettled，并注册兜底的 unhandledrejection 处理器。

  methodology · zh · reviewed · 知识截至 2026-09-15

• The JavaScript event loop: tasks, microtasks and rendering

  JavaScript runs one job at a time; the HTML event loop takes a task, then drains the whole microtask queue (promise reactions, queueMicrotask) before the next task or a rendering opportunity. Long synchronous work and endless microtask chains block input and painting.

  article · en · reviewed · 知识截至 2026-09-15

• 通过 JSON 传输 BigInt：添加 replacer 前先定义无损字段契约

  用明确的模式编码大整数，并在还原时避免悄然经过 Number 中间转换。

  article · zh · reviewed · 知识截至 2026-09-22

• 位操作基础：正确使用标志、掩码与移位

  标志是二的幂，通过 OR 组合、AND 检查、AND NOT 清除；掩码和移位用于提取字段。陷阱包括运算符优先级、有符号右移、JavaScript 固定的 32 位转换，以及 Python 无界整数。应为每个标志命名，并为每次检查加括号。

  article · zh · reviewed · 知识截至 2026-09-16

机器可读： JSON