tessl/npm-fingerprintjs--fingerprintjs

Browser fingerprinting library with the highest accuracy and stability for generating unique visitor identifiers

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Agent Management

Name: tessl/npm-fingerprintjs--fingerprintjs
Author: tessl

Agent loading and management functionality for initializing the FingerprintJS system with performance optimizations and configuration options.

Capabilities

Load Function

Creates and initializes a FingerprintJS agent instance with optional configuration.

/**
 * Builds an instance of Agent and waits for proper operation
 * @param options - Optional configuration for agent loading
 * @returns Promise resolving to initialized Agent instance
 */
function load(options?: LoadOptions): Promise<Agent>;

interface LoadOptions {
  /** 
   * Fallback delay in milliseconds for browsers without requestIdleCallback support
   * @default 50
   */
  delayFallback?: number;
  /** 
   * Whether to print debug messages to the console
   * @default false
   */
  debug?: boolean;
}

Usage Examples:

import FingerprintJS from '@fingerprintjs/fingerprintjs';

// Basic loading
const fp = await FingerprintJS.load();

// With custom delay fallback
const fp = await FingerprintJS.load({ 
  delayFallback: 100 
});

// With debug enabled
const fp = await FingerprintJS.load({ 
  debug: true 
});

Agent Class

The main agent instance that provides fingerprint generation capabilities.

interface Agent {
  /**
   * Gets the visitor identifier and associated data
   * @param options - Optional configuration for fingerprint generation
   * @returns Promise resolving to fingerprint result
   */
  get(options?: GetOptions): Promise<GetResult>;
}

interface GetOptions {
  /** 
   * Whether to print debug messages (deprecated - use debug option in load())
   * @deprecated Use the debug option of load() instead
   */
  debug?: boolean;
}

Usage Examples:

// Get fingerprint with default options
const result = await fp.get();

// Get fingerprint with debug (deprecated approach)
const result = await fp.get({ debug: true });

Loading Best Practices

Early Initialization: Load the agent as early as possible in your application lifecycle for optimal performance:

// Initialize at application startup
const fpPromise = FingerprintJS.load();

// Use later when needed
async function identifyUser() {
  const fp = await fpPromise;
  const result = await fp.get();
  return result.visitorId;
}

Browser Environment Detection: The library automatically handles different browser environments and loading contexts:

// Works in all environments
const fpPromise = FingerprintJS.load();

// Browser compatibility is handled internally
// - Uses requestIdleCallback when available
// - Falls back to setTimeout with configurable delay
// - Optimizes entropy source loading order

Performance Considerations

The delayFallback parameter controls timing for browsers without requestIdleCallback support (primarily Safari and older Edge):

// Default delay (recommended)
const fp = await FingerprintJS.load(); // Uses 50ms fallback

// Custom delay for specific use cases
const fp = await FingerprintJS.load({ 
  delayFallback: 200 // Longer delay for heavily loaded pages
});

const fp = await FingerprintJS.load({ 
  delayFallback: 10 // Shorter delay for performance-critical applications
});