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Installation

API

import * as Expo from 'expo';

expo/fetch API

expo/fetch provides a WinterCG-compliant Fetch API that works consistently across web and mobile environments, ensuring a standardized and cross-platform fetch experience within Expo applications.

import { fetch } from 'expo/fetch';

const resp = await fetch('https://httpbin.org/drip?numbytes=512&duration=2', {
  headers: { Accept: 'text/event-stream' },
});
const reader = resp.body.getReader();
const chunks = [];
while (true) {
  const { done, value } = await reader.read();
  if (done) {
    break;
  }
  chunks.push(value);
}
const buffer = new Uint8Array(chunks.reduce((acc, chunk) => acc + chunk.length, 0));
console.log(buffer.length); // 512

Note: On Android and iOS, expo/fetch is also installed as the global fetch. This means any calls to fetch(...) without importing from expo/fetch use the same WinterCG-compliant implementation. To keep React Native's built-in fetch as the global, set EXPO_PUBLIC_USE_RN_FETCH=1 in your environment variables. Named imports from expo/fetch continue to work regardless of this flag.

Encoding APIs

TextEncoder and TextDecoder are built-in APIs that provide a way to encode and decode text in various character encodings. They are available on all platforms. Refer to the browser and server runtime support for web and Node.js.

// [104, 101, 108, 108, 111]
const hello = new TextEncoder().encode('hello');

// "hello"
const text = new TextDecoder().decode(hello);

The TextEncoder API is included in the Hermes engine. See the source code in TextEncoder.cpp inside the Hermes GitHub repository.

The TextDecoder API is not spec-compliant on native platforms. Only the UTF-8 encoding is supported. If you need support for more encodings, use a polyfill like text-encoding.

The stream equivalents of these APIs, TextEncoderStream and TextDecoderStream, are also available on all platforms. They allow you to encode and decode text in a streaming manner, which is useful for processing large amounts of data without loading it all into memory at once.

const encoder = new TextEncoderStream();
const stream = new ReadableStream({
  start(controller) {
    controller.enqueue('Hello');
    controller.enqueue('World');
    controller.close();
  },
});
const reader = stream.pipeThrough(encoder).getReader();
reader.read().then(({ done, value }) => {
  console.log(value); // Uint8Array [72, 101, 108, 108, 111]
});

Streams API

Global support for standard web streams is available on native platforms to match the behavior of web and server platforms. Refer to the browser and server runtime support for specific web and Node.js support. EAS Hosting server runtime also includes support for the standard web streams API.

Globally access ReadableStream, WritableStream, and TransformStream classes.

const stream = new ReadableStream({
  start(controller) {
    controller.enqueue('Hello');
    controller.enqueue('World');
    controller.close();
  },
});
const reader = stream.getReader();
reader.read().then(({ done, value }) => {
  console.log(value); // Hello
});
reader.read().then(({ done, value }) => {
  console.log(value); // World
});

URL API

URL provides the standard API on all platforms.

On native platforms, built-in URL and URLSearchParams implementations replace the shims in react-native. Refer to the browser and server runtime support for web and Node.js.

const url = new URL('https://expo.dev');

const params = new URLSearchParams();

Expo's built-in URL support attempts to be fully spec compliant. The only missing exception is that native platforms do not currently support non-ASCII characters in the hostname.

console.log(new URL('http://🥓').toString());

// This outputs the following:
// - Web, Node.js: http://xn--pr9h/
// - Android, iOS: http://🥓/

structuredClone

structuredClone is a built-in function that allows you to create a deep copy of a value, including complex objects like Map, Set, and ArrayBuffer. It is available on all platforms.

const original = { name: 'Expo', date: new Date() };
const clone = structuredClone(original);
console.log(clone); // { name: 'Expo', date: Date }

The transfer option for ArrayBuffer and TypedArrays is not implemented.

Remove any custom polyfills for structuredClone to prevent bloat. Refer to the standard documentation for more information on the structured clone algorithm.

No API data file found, sorry!

Common questions

Some common questions about using the expo package in your project.

  @Override
  protected String getMainComponentName() {
+    return "main";
  }

{
  "main": "src/main.jsx"
}

import { registerRootComponent } from 'expo';
import { View } from 'react-native';

function App() {
  return <View />;
}

registerRootComponent(App);