Azion unenv Preset

A preset configuration for unenv that provides polyfills and environment compatibility for Azion Edge Runtime.

Usage

The preset can be used with unenv to provide compatibility between Node.js and Azion Edge Runtime environments:

import { preset } from '@azion/unenv-preset'
// Use with unenv
export default {
  preset: preset
}

Features

Node.js Polyfills

This preset provides polyfills for common Node.js APIs to ensure compatibility when running code in the Azion Edge Runtime environment. The following modules are polyfilled:

Module	Description
`crypto`	Complete cryptographic functionality including hashing, encryption, and UUID generation.
`events`	Event handling through `events/events.js`.
`http`	HTTP client functionality via `stream-http`.
`module`	Basic module system compatibility (limited functionality).
`stream`	Stream implementations via `stream-browserify`.
`string_decoder`	String decoding utilities.
`url`	URL parsing and formatting.
`util`	Utility functions.
`timers`	Timer functions via `timers-browserify`.
`vm`	Virtual Machine functionality via `vm-browserify`.
`zlib`	Compression functionality via `browserify-zlib`.

Example:

This exemple is using the crypto polyfill.

import { createHash, randomUUID } from '@azion/unenv-preset/polyfills/node/crypto'

// Create a hash
const hash = createHash('sha256')
hash.update('some data')
console.log(hash.digest('hex'))

// Generate a UUID
const uuid = randomUUID()

File System Polyfills

The preset includes comprehensive file system polyfills that mirror Node.js’s fs module functionality. These polyfills work with an in-memory file system when running in the Edge Runtime.

Basic File Operations

import { readFileSync, writeFileSync } from '@azion/unenv-preset/polyfills/node/fs'
// Read a file
const content = readFileSync('/path/to/file.txt', 'utf8')
// Write to a file
writeFileSync('/path/to/new-file.txt', 'Hello World', 'utf8')

Directory Operations

import { readdirSync, mkdirSync } from '@azion/unenv-preset/polyfills/node/fs'

// List directory contents
const files = readdirSync('/path/to/dir')

// Create a directory
mkdirSync('/path/to/new-dir')

File Stats and Information

import { statSync, existsSync } from '@azion/unenv-preset/polyfills/node/fs'

// Check if file exists
if (existsSync('/path/to/file.txt')) {
  // Get file stats
  const stats = statSync('/path/to/file.txt')
  console.log(`File size: ${stats.size}`)
  console.log(`Is directory: ${stats.isDirectory()}`)
  console.log(`Is file: ${stats.isFile()}`)
}

File Descriptors

import { openSync, closeSync, readSync } from '@azion/unenv-preset/polyfills/node/fs'

// Open file and get file descriptor
const fd = openSync('/path/to/file.txt', 'r')

// Read from file descriptor
const buffer = Buffer.alloc(1024)
readSync(fd, buffer, 0, 1024, 0)

// Close file descriptor
closeSync(fd)

Global Polyfills

The preset also provides polyfills for Node.js global variables and objects:

Global Object	Description
`__dirname`	Current directory name.
`__filename`	Current file name.
`process`	Process information and environment (including env variables).
`performance`	Performance timing functionality.
`navigator`	Browser-compatible navigator object.

The preset also handles injection of these globals through the unenv configuration:

import { preset } from '@azion/unenv-preset'

// Preset configuration automatically injects globals
export default {
  inject: {
    __dirname: preset.inject.__dirname,
    __filename: preset.inject.__filename,
    process: preset.inject.process,
    performance: preset.inject.performance,
    navigator: preset.inject.navigator
  }
}

API Reference

getFileContent

Decodes file content and returns it as either a Buffer or string.

Parameters:

Parameter	Description	Values
`file`	The file object containing content in base64 format.	—
`returnBuffer`	Determines return type (default: `true`).	`true` → Returns a Buffer,`false` → Returns a string.

Returns:

Return Type	Description
`Buffer \| string`	The decoded file content.

Example:

const fileBuffer = getFileContent(file) // returns Buffer
const fileString = getFileContent(file, false) // returns string

closeSync

Synchronously closes the file descriptor.

Parameters:

Parameter	Description
`fd`	The file descriptor to close.

Example:

closeSync(fd)

openSync

Synchronously opens a file.

Parameters:

Parameter	Description
`path`	The path to the file.
`flags`	The opening mode (for example, ‘r’, ‘w’).
`mode`	(Optional) The file mode.

Returns:

Return Type	Description
`number`	The file descriptor.

Example:

const fd = openSync('/path/to/file.txt', 'r')

statSync

Synchronously retrieves the fs.Stats for the specified path.

Parameters:

Parameter	Description
`path`	The path to the file or directory.
`options`	(Optional) Options for the stat call.

Returns:

Return Type	Description
`fs.Stats`	The stats object for the file or directory.

Example:

const stats = statSync('/path/to/file.txt')

readFileSync

Synchronously reads the entire contents of a file.

Parameters:

Parameter	Description
`path`	The file path.
`options`	(Optional) Options for reading the file.

Returns:

Return Type	Description
`string \| Buffer`	The file contents.

Example:

const content = readFileSync('/path/to/file.txt', 'utf8')

readdirSync

Synchronously reads the contents of a directory.

Parameters:

Parameter	Description
`path`	The directory path.
`options`	(Optional) Options for reading the directory.

Returns:

Return Type	Description
`string[]`	An array of file names in the directory.

Example:

const files = readdirSync('/path/to/dir')