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React Native AIby Callstack

Polyfills

The AI SDK uses a few web APIs that React Native doesn’t have, such as text encoding streams and structuredClone. Add them once, before anything else in your app runs.

Expo

Section titled “Expo”

First, install the following packages:

Terminal window
npm install @ungap/structured-clone @stardazed/streams-text-encoding

Then create a polyfills.js file in the root of your project:

polyfills.js
import { Platform } from 'react-native'
import structuredClone from '@ungap/structured-clone'


if (Platform.OS !== 'web') {
  // require, not import: it runs synchronously, before the rest of the app,
  // and keeps React Native internals out of the web build.
  const {
    polyfillGlobal,
  } = require('react-native/Libraries/Utilities/PolyfillFunctions')
  const {
    TextEncoderStream,
    TextDecoderStream,
  } = require('@stardazed/streams-text-encoding')


  if (!('structuredClone' in global)) {
    polyfillGlobal('structuredClone', () => structuredClone)
  }


  polyfillGlobal('TextEncoderStream', () => TextEncoderStream)
  polyfillGlobal('TextDecoderStream', () => TextDecoderStream)
}


export {}

Import it first in your app’s entry point, such as index.js or App.tsx:

import './polyfills'

Bare React Native

Section titled “Bare React Native”

Without Expo, you also need web streams, which Expo provides.

First, install the following packages:

Terminal window
npm install @ungap/structured-clone @stardazed/streams-text-encoding web-streams-polyfill

Then create a polyfills.js file in the root of your project:

polyfills.js
import { Platform } from 'react-native'
import structuredClone from '@ungap/structured-clone'
import {
  TransformStream,
  ReadableStream,
  WritableStream,
} from 'web-streams-polyfill'


if (Platform.OS !== 'web') {
  // require, not import: it runs synchronously, before the rest of the app,
  // and keeps React Native internals out of the web build.
  const {
    polyfillGlobal,
  } = require('react-native/Libraries/Utilities/PolyfillFunctions')
  const {
    TextEncoderStream,
    TextDecoderStream,
  } = require('@stardazed/streams-text-encoding')


  if (!('structuredClone' in global)) {
    polyfillGlobal('structuredClone', () => structuredClone)
  }


  if (!('TransformStream' in global)) {
    polyfillGlobal('TransformStream', () => TransformStream)
  }


  if (!('ReadableStream' in global)) {
    polyfillGlobal('ReadableStream', () => ReadableStream)
  }


  if (!('WritableStream' in global)) {
    polyfillGlobal('WritableStream', () => WritableStream)
  }


  polyfillGlobal('TextEncoderStream', () => TextEncoderStream)
  polyfillGlobal('TextDecoderStream', () => TextDecoderStream)
}


export {}

Import it first in your app’s entry point, such as index.js or App.tsx:

import './polyfills'
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