Janus Client SDK

A lightweight JavaScript library for tracking events from web applications. Automatically handles batching, retries, rate limiting, and persistence.

Lightweight (~3KB)Auto RetryBatchingPersistence

API Reference

Janus.init(apiKey, options)#

Initialize the SDK. Must be called before any tracking.

Parameter	Type	Required	Description
apiKey	string	Yes	Your Janus API key (starts with jns_)
options.batchInterval	number	No	Flush interval in ms (default: 1000)
options.batchSize	number	No	Events to trigger immediate flush (default: 10)
options.debug	boolean	No	Enable debug logging (default: false)
options.persistQueue	boolean	No	Persist queue to localStorage (default: true)
options.trackPageViews	boolean	No	Auto-track page views on init (default: true)
options.trackSPANavigation	boolean	No	Auto-track SPA route changes (default: true)
options.onError	function	No	Callback for SDK errors: function(type, details)

javascript

Janus.init('jns_your_api_key_here', {
    batchInterval: 2000,  // Flush every 2 seconds
    batchSize: 20,        // Or when 20 events queued
    debug: true           // Enable console logging
});

Janus.track(eventName, properties)#

Track a custom event.

Parameter	Type	Required	Description
eventName	string	Yes	Name of the event
properties	object	No	Additional event properties

javascript

Janus.track('purchase_completed', {
    orderId: 'ORD-123',
    amount: 99.99,
    currency: 'USD',
    items: ['item1', 'item2']
});

Janus.page(pageName, properties)#

Track a page view. Called automatically on init and during SPA navigation by default. Use this for manual tracking or to pass custom page names/properties.

Parameter	Type	Required	Description
pageName	string	No	Name of the page (defaults to document.title)
properties	object	No	Additional properties

javascript

// Simple page view
Janus.page();

// Named page view with properties
Janus.page('Product Details', {
    productId: 'SKU-123',
    category: 'Electronics'
});

Janus.identify(userId, traits)#

Identify a user. Links all future events to this user ID.

Parameter	Type	Required	Description
userId	string	Yes	Unique user identifier
traits	object	No	User traits/properties

javascript

Janus.identify('user_12345', {
    email: 'user@example.com',
    name: 'John Doe',
    plan: 'pro',
    signupDate: '2024-01-15'
});

Janus.reset()#

Reset user identity. Call this on logout to generate new anonymous IDs.

javascript

// On user logout
function logout() {
    Janus.reset();
    // ... rest of logout logic
}

Janus.flush()#

Manually flush the event queue. Returns a Promise.

javascript

// Force send all queued events
await Janus.flush();

Janus.getConfig()#

Get current SDK configuration (useful for debugging).

javascript

console.log(Janus.getConfig());
// {
//   batchInterval: 1000,
//   batchSize: 10,
//   apiKey: 'jns_abc123...',
//   distinctId: 'user_xyz',
//   sessionId: 'sess_abc',
//   queueLength: 3,
//   isInitialized: true
// }

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If you have questions or run into issues, check out our troubleshooting guide or reach out to our support team.

Troubleshooting Guide