API

Web API

除了 ECMAScript 标准库，nsh 应用的 JS 环境还提供一组 Web 平台全局对象：fetch 及其 Headers、Request、Response；Streams 标准；URL 和 URLSearchParams；TextEncoder / TextDecoder；Blob、File 和 FormData；EventTarget、Event 和 AbortController；定时器、requestAnimationFrame 和 console。它们都用 Rust 原生实现，遵循 WHATWG 标准，无需 import。很多为浏览器编写的库（HTTP 客户端、URL 与编码工具、流处理工具）可以直接使用。

这里没有 DOM：没有 window、document、localStorage、XMLHttpRequest、WebSocket、crypto，也没有 structuredClone。界面用元素和组件搭建，而不是 HTML。

这些全局对象的 TypeScript 声明会生成到 .nsh/types/nsh/globals.d.ts（见项目结构）。

分组	全局对象
控制台与计时	`console`、`performance`
定时器与帧	`setTimeout`、`setInterval`、`clearTimeout`、`clearInterval`、`queueMicrotask`、`requestAnimationFrame`、`cancelAnimationFrame`
Base64 与错误	`atob`、`btoa`、`DOMException`
事件与中止信号	`EventTarget`、`Event`、`CustomEvent`、`AbortController`、`AbortSignal`
URL	`URL`、`URLSearchParams`
文本编码	`TextEncoder`、`TextDecoder`
Blob 与表单数据	`Blob`、`File`、`FormData`
Fetch	`fetch`、`Headers`、`Request`、`Response`
流	`ReadableStream`、`WritableStream`、`TransformStream`、各类 reader、writer 和 controller、`ByteLengthQueuingStrategy`、`CountQueuingStrategy`、`TextEncoderStream`、`TextDecoderStream`

#控制台与计时

declare var console: {
  log(...data: unknown[]): void;
  info(...data: unknown[]): void;
  debug(...data: unknown[]): void;
  warn(...data: unknown[]): void;
  error(...data: unknown[]): void;
};

declare var performance: {
  /** Milliseconds since the JS context started, with sub-millisecond precision. */
  now(): number;
};

console 每次调用向运行时日志（target 为 js）写一行：log 和 info 为 info 级别，debug、warn、error 为各自的级别。多个参数以空格连接；字符串原样输出，错误对象带调用栈，函数输出为 [Function name]，对象和数组输出为 JSON（遇到循环引用时退回 String(value)）。

设备连接开发服务器期间，日志会出现在运行 nsh run / nsh dev 的终端里，并带上设备名前缀，参见开发服务器与调试。

performance.now() 就是 requestAnimationFrame 传给回调的那个时钟。performance 没有其他成员。

#定时器与帧

function setTimeout(handler: (...args: any[]) => void, timeout?: number, ...args: any[]): number;
function setInterval(handler: (...args: any[]) => void, timeout?: number, ...args: any[]): number;
function clearTimeout(id: number | undefined): void;
function clearInterval(id: number | undefined): void;
function queueMicrotask(callback: () => void): void;
/** Runs `callback` at the next display frame with its time in milliseconds. */
function requestAnimationFrame(callback: (time: number) => void): number;
function cancelAnimationFrame(id: number): void;

定时器的行为与浏览器一致：缺省、负数或非有限的延迟视为 0，返回的 id 是正整数，清除不存在的 id 不会报错。handler 必须是函数（不会执行字符串形式的代码）。嵌套定时器不会被钳制到 4 ms。

requestAnimationFrame 的回调在引擎产出下一帧时执行一次，同一帧的回调拿到相同的 performance.now() 时间。回调里再次请求的帧会在下一帧调用，所以常见的循环写法可以正常工作：

let start = 0;
function tick(time: number) {
  if (!start) start = time;
  progress.set(Math.min(1, (time - start) / 300));
  if (time - start < 300) requestAnimationFrame(tick);
}
requestAnimationFrame(tick);

#Base64 与错误

function atob(data: string): string;
function btoa(data: string): string;

class DOMException extends Error {
  constructor(message?: string, name?: string);
  readonly name: string;
  readonly message: string;
  readonly code: number;
}

atob / btoa 与浏览器一样，在二进制字符串和 Base64 之间转换。DOMException 是被中止的操作所 reject 的值：不带 reason 调用 AbortController.abort() 得到名为 "AbortError" 的 DOMException，AbortSignal.timeout 得到名为 "TimeoutError" 的。

#事件与中止信号

class EventTarget {
  constructor();
  addEventListener(type: string, listener: EventListenerOrEventListenerObject | null,
    options?: AddEventListenerOptions | boolean): void;
  removeEventListener(type: string, listener: EventListenerOrEventListenerObject | null,
    options?: { capture?: boolean } | boolean): void;
  dispatchEvent(event: Event): boolean;
}

interface AddEventListenerOptions {
  capture?: boolean;
  once?: boolean;
  passive?: boolean;
  signal?: AbortSignal;
}

class Event {
  constructor(type: string, init?: { bubbles?: boolean; cancelable?: boolean; composed?: boolean });
  readonly type: string;
  readonly target: EventTarget | null;
  readonly currentTarget: EventTarget | null;
  readonly eventPhase: number; // NONE 0, CAPTURING_PHASE 1, AT_TARGET 2, BUBBLING_PHASE 3
  readonly bubbles: boolean;
  readonly cancelable: boolean;
  readonly defaultPrevented: boolean;
  readonly composed: boolean;
  readonly isTrusted: boolean;
  readonly timeStamp: number;
  returnValue: boolean;
  cancelBubble: boolean;
  readonly srcElement: EventTarget | null; // legacy: `target`
  initEvent(type: string, bubbles?: boolean, cancelable?: boolean): void; // legacy
  composedPath(): EventTarget[];
  preventDefault(): void;
  stopPropagation(): void;
  stopImmediatePropagation(): void;
}

class CustomEvent<T = any> extends Event {
  constructor(type: string, init?: EventInit & { detail?: T });
  readonly detail: T;
}

class AbortController {
  readonly signal: AbortSignal;
  abort(reason?: any): void;
}

class AbortSignal extends EventTarget {
  readonly aborted: boolean;
  readonly reason: any;
  onabort: ((event: Event) => void) | null;
  throwIfAborted(): void;
  static abort(reason?: any): AbortSignal;
  static timeout(milliseconds: number): AbortSignal;
  static any(signals: Iterable<AbortSignal>): AbortSignal;
}

这些就是 DOM 标准里的类，只有一处不同：没有节点树，事件只派发给目标本身。先执行捕获监听器，再执行其他监听器，与 DOM 在目标阶段的行为一致；bubbles 不起作用。这些类可以被继承，所以 EventTarget 可以当作一个小型事件发射器：

class Channel extends EventTarget {
  send(message: string) {
    this.dispatchEvent(new CustomEvent("message", { detail: message }));
  }
}

const channel = new Channel();
channel.addEventListener("message", (e) => console.log((e as CustomEvent<string>).detail));
channel.send("hello");

它们与元素的事件（onPress、onChangeText 等）无关，后者是 props，参见触摸与手势。

AbortSignal 可以取消 fetch 请求和流的管道传输，也可以移除用 { signal } 添加的监听器：

const controller = new AbortController();
const signal = AbortSignal.any([controller.signal, AbortSignal.timeout(10_000)]);
fetch("https://api.example.com/search?q=nsh", { signal }).catch((e) => {
  if (e.name === "AbortError" || e.name === "TimeoutError") return;
  throw e;
});
// later, for example when the screen closes:
controller.abort();

#URL

class URL {
  constructor(url: string | URL, base?: string | URL);
  static canParse(url: string | URL, base?: string | URL): boolean;
  static parse(url: string | URL, base?: string | URL): URL | null;
  /** A `blob:` URL `fetch` reads `blob` from, until revoked. */
  static createObjectURL(blob: Blob): string;
  static revokeObjectURL(url: string): void;
  href: string;
  readonly origin: string;
  protocol: string;
  username: string;
  password: string;
  host: string;
  hostname: string;
  port: string;
  pathname: string;
  search: string;
  hash: string;
  readonly searchParams: URLSearchParams;
  toString(): string;
  toJSON(): string;
}

class URLSearchParams {
  constructor(init?: string | Record<string, string> | Iterable<[string, string]> | URLSearchParams);
  readonly size: number;
  append(name: string, value: string): void;
  delete(name: string, value?: string): void;
  get(name: string): string | null;
  getAll(name: string): string[];
  has(name: string, value?: string): boolean;
  set(name: string, value: string): void;
  sort(): void;
  forEach(callback: (value: string, key: string, parent: URLSearchParams) => void, thisArg?: unknown): void;
  entries(): IterableIterator<[string, string]>;
  keys(): IterableIterator<string>;
  values(): IterableIterator<string>;
  [Symbol.iterator](): IterableIterator<[string, string]>;
  toString(): string;
}

URL 按 URL 标准解析。searchParams 是双向联动的：修改参数会重写查询串，设置 search 或 href 会重新解析参数。

const url = new URL("/v1/items", "https://api.example.com");
url.searchParams.set("page", "2");
url.searchParams.append("tag", "new");
url.href; // "https://api.example.com/v1/items?page=2&tag=new"

URLSearchParams（以及 Headers、FormData）的迭代器遍历的是创建迭代器那一刻的快照，并且带有迭代器辅助方法（map、filter、toArray 等）。

URL.createObjectURL(blob) 返回一个 blob: URL，在调用 revokeObjectURL 之前都可以用 fetch（GET）读取。只有 fetch 认识这种 URL，<Image> 等元素不认识。

#文本编码

class TextEncoder {
  readonly encoding: "utf-8";
  encode(input?: string): Uint8Array;
  encodeInto(source: string, destination: Uint8Array): { read: number; written: number };
}

/** UTF-8, UTF-16LE / BE and windows-1252 (with the labels of latin1 and ASCII). */
class TextDecoder {
  constructor(label?: string, options?: { fatal?: boolean; ignoreBOM?: boolean });
  readonly encoding: string;
  readonly fatal: boolean;
  readonly ignoreBOM: boolean;
  decode(input?: BufferSource, options?: { stream?: boolean }): string;
}

TextDecoder 支持的编码比浏览器少：UTF-8、UTF-16LE、UTF-16BE 和 windows-1252（按 Encoding 标准，latin1、iso-8859-1、ascii 等标签也指向它）。其他标签会抛出 RangeError。传入 { stream: true } 时，被切断在两个分块之间的多字节序列会保留到下一次调用。

#Blob 与表单数据

class Blob {
  constructor(blobParts?: Iterable<BlobPart>, options?: { type?: string; endings?: "transparent" | "native" });
  readonly size: number;
  readonly type: string;
  slice(start?: number, end?: number, contentType?: string): Blob;
  arrayBuffer(): Promise<ArrayBuffer>;
  bytes(): Promise<Uint8Array>;
  text(): Promise<string>;
  stream(): ReadableStream<Uint8Array>;
}

class File extends Blob {
  constructor(fileBits: Iterable<BlobPart>, fileName: string,
    options?: { type?: string; endings?: "transparent" | "native"; lastModified?: number });
  readonly name: string;
  readonly lastModified: number;
  readonly webkitRelativePath: string;
}

class FormData {
  constructor();
  append(name: string, value: string | Blob, fileName?: string): void;
  delete(name: string): void;
  get(name: string): File | string | null;
  getAll(name: string): (File | string)[];
  has(name: string): boolean;
  set(name: string, value: string | Blob, fileName?: string): void;
  forEach(callback: (value: File | string, key: string, parent: FormData) => void, thisArg?: unknown): void;
  entries(): IterableIterator<[string, File | string]>;
  keys(): IterableIterator<string>;
  values(): IterableIterator<File | string>;
  [Symbol.iterator](): IterableIterator<[string, File | string]>;
}

type BlobPart = ArrayBuffer | ArrayBufferView | Blob | string;

Blob 的字节保存在内存中，slice 共享这些字节而不是复制。Blob 只是内存中的值：File 背后没有文件系统访问，FormData 也没有从表单元素构造的方式。

FormData 作为请求体时以 multipart/form-data 发送；Response.formData() / Request.formData() 能解析 multipart/form-data 和 application/x-www-form-urlencoded。

const form = new FormData();
form.append("title", "Holiday");
form.append("photo", new Blob([bytes], { type: "image/jpeg" }), "photo.jpg");
await fetch("https://api.example.com/upload", { method: "POST", body: form });

#Fetch

/**
 * HTTP through the platform's network stack (NSURLSession,
 * HttpURLConnection), streaming both ways; `data:` and `blob:` URLs are
 * answered locally.
 */
function fetch(input: string | URL | Request, init?: RequestInit): Promise<Response>;

interface RequestInit {
  method?: string;
  headers?: HeadersInit;
  /** A ReadableStream is sent as it is read (chunked), with `duplex: "half"`. */
  body?: BodyInit | null;
  duplex?: "half";
  signal?: AbortSignal | null;
  /** "manual" gives the 3xx response itself. */
  redirect?: "follow" | "manual" | "error";
  credentials?: "omit" | "same-origin" | "include";
  cache?: "default" | "no-store" | "reload" | "no-cache" | "force-cache" | "only-if-cached";
  mode?: "same-origin" | "no-cors" | "cors";
  referrer?: string;
  referrerPolicy?: string;
  integrity?: string;
  keepalive?: boolean;
  priority?: "high" | "low" | "auto";
}

type HeadersInit = Headers | Record<string, string> | Iterable<[string, string]>;
type BodyInit = ReadableStream<Uint8Array> | Blob | BufferSource | FormData | URLSearchParams | string;

fetch 通过平台自身的网络栈发送 HTTP 和 HTTPS 请求：iOS 和 Mac Catalyst 上是 NSURLSession，Android 上是 HttpURLConnection。因此系统的代理设置、TLS 配置和证书信任都会生效。data: URL 和 blob: URL（来自 URL.createObjectURL）在本地直接应答，不经过网络；其他协议一律 reject。

type Todo = { id: number; title: string; done: boolean };

async function loadTodos(): Promise<Todo[]> {
  const res = await fetch("https://api.example.com/todos", {
    headers: { Authorization: `Bearer ${token}` },
  });
  if (!res.ok) throw new Error(`HTTP ${res.status}`);
  return res.json();
}

#Headers、Request 和 Response

class Headers {
  constructor(init?: HeadersInit);
  append(name: string, value: string): void;
  delete(name: string): void;
  get(name: string): string | null;
  getSetCookie(): string[];
  has(name: string): boolean;
  set(name: string, value: string): void;
  forEach(callback: (value: string, key: string, parent: Headers) => void, thisArg?: unknown): void;
  entries(): IterableIterator<[string, string]>;
  keys(): IterableIterator<string>;
  values(): IterableIterator<string>;
  [Symbol.iterator](): IterableIterator<[string, string]>;
}

interface Body {
  /** The body as it arrives (a byte stream), or null. */
  readonly body: ReadableStream<Uint8Array> | null;
  readonly bodyUsed: boolean;
  arrayBuffer(): Promise<ArrayBuffer>;
  blob(): Promise<Blob>;
  bytes(): Promise<Uint8Array>;
  formData(): Promise<FormData>;
  json(): Promise<any>;
  text(): Promise<string>;
}

class Request implements Body {
  constructor(input: string | URL | Request, init?: RequestInit);
  readonly method: string;
  readonly url: string;
  readonly headers: Headers;
  readonly destination: string;
  readonly referrer: string;
  readonly referrerPolicy: string;
  readonly mode: string;
  readonly credentials: string;
  readonly cache: string;
  readonly redirect: "follow" | "manual" | "error";
  readonly integrity: string;
  readonly keepalive: boolean;
  readonly isReloadNavigation: boolean;
  readonly isHistoryNavigation: boolean;
  readonly signal: AbortSignal;
  readonly duplex: "half";
  clone(): Request;
  // ...and the Body members
}

class Response implements Body {
  constructor(body?: BodyInit | null, init?: { status?: number; statusText?: string; headers?: HeadersInit });
  static json(data: unknown, init?: ResponseInit): Response;
  static error(): Response;
  static redirect(url: string | URL, status?: number): Response;
  readonly type: "basic" | "default" | "error";
  readonly url: string;
  readonly redirected: boolean;
  readonly status: number;
  readonly ok: boolean;
  readonly statusText: string;
  readonly headers: Headers;
  clone(): Response;
  // ...and the Body members
}

#流式传输

响应的 body 是一个字节流，网络每交付一段数据就填充一段，所以大的或长连接的响应（下载、server-sent events、流式输出的模型结果）可以边到达边处理。未读取的数据超过 1 MiB 时，请求会暂停，直到应用继续读取。

const res = await fetch("https://api.example.com/events");
const lines = res.body!.pipeThrough(new TextDecoderStream());
for await (const chunk of lines) {
  console.log(chunk);
}

请求体是 ReadableStream 时，会随网络栈的需要逐块上传；按 Fetch 标准的要求，需要传 duplex: "half"：

await fetch("https://api.example.com/upload", {
  method: "PUT",
  body: blob.stream(),
  duplex: "half",
});

#与浏览器的差异

没有 CORS，也没有 origin。 应用不是网页：它可以访问能力声明允许的任何主机。mode 会被接受但被忽略。
没有禁止设置的请求头。 应用可以设置 Cookie、User-Agent、Origin 等任意请求头。未指定 Accept 时会发送 Accept: */*。
redirect: "manual" 直接交付 3xx 响应本身，带有状态码和 Location 头，而不是不透明的过滤响应。"follow" 会跟随重定向（每一跳都按能力声明检查）；"error" 在响应为重定向时 reject。
FormData 请求体总是使用 Content-Type: multipart/form-data; boundary=…，即使已经设置了 Content-Type 头。HTTP 库常常先设一个默认类型，只在检测到浏览器时才清除；缺少 boundary，服务器就无法解析请求体。
credentials、cache、referrer、referrerPolicy、integrity、keepalive 和 priority 会被校验并保存在 Request 对象上，但不会传给网络栈：缓存和 Cookie 的处理遵循平台网络栈自身的行为。
能力声明。 当应用在 nsh.json 中声明了 network 能力（或嵌入它的宿主应用授予的更少）时，访问未被允许的主机的请求根本不会发到网络，fetch 以 TypeError reject。参见沙箱与能力。
错误。 网络失败以 TypeError reject，消息以 Network request failed: 开头；中止则以 signal 的 reason reject。

在组件中加载数据的完整指南见网络。

#流

完整实现了 WHATWG Streams 标准：可读流（默认流和字节流、BYOB reader、tee、pipeTo / pipeThrough、ReadableStream.from、异步迭代）、可写流、转换流、两种排队策略以及文本编码流。

class ReadableStream<R = any> {
  constructor(underlyingSource: UnderlyingByteSource, strategy?: { highWaterMark?: number });
  constructor(underlyingSource?: UnderlyingDefaultSource<R>, strategy?: QueuingStrategy<R>);
  static from<R>(iterable: Iterable<R | PromiseLike<R>> | AsyncIterable<R>): ReadableStream<R>;
  readonly locked: boolean;
  cancel(reason?: any): Promise<void>;
  getReader(options: { mode: "byob" }): ReadableStreamBYOBReader;
  getReader(): ReadableStreamDefaultReader<R>;
  pipeThrough<T>(transform: { writable: WritableStream<R>; readable: ReadableStream<T> },
    options?: StreamPipeOptions): ReadableStream<T>;
  pipeTo(destination: WritableStream<R>, options?: StreamPipeOptions): Promise<void>;
  tee(): [ReadableStream<R>, ReadableStream<R>];
  values(options?: { preventCancel?: boolean }): AsyncIterableIterator<R>;
  [Symbol.asyncIterator](options?: { preventCancel?: boolean }): AsyncIterableIterator<R>;
}

class ReadableStreamDefaultReader<R = any> {
  constructor(stream: ReadableStream<R>);
  readonly closed: Promise<void>;
  read(): Promise<{ done: false; value: R } | { done: true; value?: R }>;
  releaseLock(): void;
  cancel(reason?: any): Promise<void>;
}

class ReadableStreamBYOBReader {
  constructor(stream: ReadableStream<Uint8Array>);
  readonly closed: Promise<void>;
  read<T extends ArrayBufferView>(view: T, options?: { min?: number }): Promise<ReadableStreamReadResult<T>>;
  releaseLock(): void;
  cancel(reason?: any): Promise<void>;
}

class ReadableStreamDefaultController<R = any> {
  readonly desiredSize: number | null;
  close(): void;
  enqueue(chunk?: R): void;
  error(e?: any): void;
}

class ReadableByteStreamController {
  readonly byobRequest: ReadableStreamBYOBRequest | null;
  readonly desiredSize: number | null;
  close(): void;
  enqueue(chunk: ArrayBufferView): void;
  error(e?: any): void;
}

class ReadableStreamBYOBRequest {
  readonly view: ArrayBufferView | null;
  respond(bytesWritten: number): void;
  respondWithNewView(view: ArrayBufferView): void;
}

class WritableStream<W = any> {
  constructor(underlyingSink?: UnderlyingSink<W>, strategy?: QueuingStrategy<W>);
  readonly locked: boolean;
  abort(reason?: any): Promise<void>;
  close(): Promise<void>;
  getWriter(): WritableStreamDefaultWriter<W>;
}

class WritableStreamDefaultWriter<W = any> {
  constructor(stream: WritableStream<W>);
  readonly closed: Promise<void>;
  readonly desiredSize: number | null;
  readonly ready: Promise<void>;
  abort(reason?: any): Promise<void>;
  close(): Promise<void>;
  releaseLock(): void;
  write(chunk?: W): Promise<void>;
}

class WritableStreamDefaultController {
  readonly signal: AbortSignal;
  error(e?: any): void;
}

class TransformStream<I = any, O = any> {
  constructor(transformer?: Transformer<I, O>, writableStrategy?: QueuingStrategy<I>,
    readableStrategy?: QueuingStrategy<O>);
  readonly readable: ReadableStream<O>;
  readonly writable: WritableStream<I>;
}

class TransformStreamDefaultController<O = any> {
  readonly desiredSize: number | null;
  enqueue(chunk?: O): void;
  error(reason?: any): void;
  terminate(): void;
}

class ByteLengthQueuingStrategy {
  constructor(init: { highWaterMark: number });
  readonly highWaterMark: number;
  readonly size: (chunk: ArrayBufferView) => number;
}

class CountQueuingStrategy {
  constructor(init: { highWaterMark: number });
  readonly highWaterMark: number;
  readonly size: (chunk: any) => 1;
}

class TextEncoderStream {
  readonly encoding: "utf-8";
  readonly readable: ReadableStream<Uint8Array>;
  readonly writable: WritableStream<string>;
}

class TextDecoderStream {
  constructor(label?: string, options?: { fatal?: boolean; ignoreBOM?: boolean });
  readonly encoding: string;
  readonly fatal: boolean;
  readonly ignoreBOM: boolean;
  readonly readable: ReadableStream<string>;
  readonly writable: WritableStream<BufferSource>;
}

底层 source、sink 和 transformer 对象（UnderlyingDefaultSource、UnderlyingByteSource、UnderlyingSink、Transformer）以及 StreamPipeOptions（preventAbort、preventCancel、preventClose、signal）的结构与标准一致，完整声明见 globals.d.ts。

TextEncoderStream 会把被切断在两个字符串分块之间的代理对拼回一个字符，TextDecoderStream 会把切断在两个字节分块之间的多字节序列拼回完整字符。

一个把文本按行切分的转换流：

function lines(): TransformStream<string, string> {
  let rest = "";
  return new TransformStream({
    transform(chunk, controller) {
      const parts = (rest + chunk).split("\n");
      rest = parts.pop()!;
      for (const line of parts) controller.enqueue(line);
    },
    flush(controller) {
      if (rest) controller.enqueue(rest);
    },
  });
}

const res = await fetch("https://api.example.com/log");
for await (const line of res.body!.pipeThrough(new TextDecoderStream()).pipeThrough(lines())) {
  console.log(line);
}

#性能

这些类都是原生实现的：解析 URL、编解码文本、构建 multipart 请求体、搬运流的分块，都在 Rust 中完成，而不是在 QuickJS 里。不过 JS 的每次调用都要进入运行时，所以请优先使用整块缓冲区的操作（res.json()、res.text()、encoder.encode(s)），避免在 JS 里逐字节循环。参见性能。