The following sections cover the finer technical details of the improvements in the RudderStack JavaScript SDK that make it more efficient and easier to use.

sendBeacon as a transport mechanism

The JavaScript SDK hosted at https://cdn.rudderlabs.com/v1.1/rudder-analytics.min.js sends the event payload using the XHR (XMLHttpRequest) API.

RudderStack now also supports sending the event payload using the navigator.sendBeacon browser utility, which asynchronously sends a small amount of data over HTTP to the RudderStack server. The JavaScript SDK supports a new Boolean field, useBeacon, in the load() call options. When set to true, the SDK sends events using the navigator.sendBeacon utility.

Why use sendBeacon to send your event payload?

There are two key advantages of using the navigator.sendBeacon utility to send your event payload:

• Since pushing events to the Beacon queue is faster compared to the XHR instrumentation, you may see some performance improvements in the JavaScript SDK.
• The Beacon requests are optimized so that the browser waits until the CPU load is lower, or until the network is free before making the actual requests. This can lead to better website performance.

BeaconQueueOpts

The JavaScript SDK internally uses a separate queue (BeaconQueueOpts) to hold the data and send it through the sendBeacon utility in batches. The structure of BeaconQueueOpts is shown below:

Copy
{
  maxItems: 10 
  flushQueueInterval: 600000
}

Event delivery guarantees and retry mechanism

This section highlights some important considerations before you opt to use sendBeacon for sending your event payload:

• The Beacon requests sent from the SDK using navigator.sendBeacon() only push the events to browser’s Beacon queue. As it depends on the browser's engine to send these events from the queue, RudderStack cannot guarantee the events getting discarded due to 5xx errors and other network-related errors (request timed out, end resource unavailable, etc.).

• The Beacon queue maintained by the browsers also has a limitation on the total size of the elements present in the queue at any point, and peaks out at 64 KB. Therefore, you cannot send high frequency hits from the main thread in one go, as the Beacon queue cannot take up cycles to dequeue itself. The JavaScript SDK handles this by maintaining a separate queue which retries pushing events to the Beacon queue in case they are not successfully pushed in the first attempt.

Reduced core SDK size by calling requireIntegration

As RudderStack supports more native destinations through the JavaScript SDK, more instrumentation code gets added to it. This leads to an increase in the SDK size and requires the browser to evaluate and parse more unused JavaScript.

Therefore, we have decided to not bundle these instrumentation codes for the end destinations in the core JavaScript SDK. Instead, the SDK will now only fetch the destination configuration settings from the RudderStack dashboard such as track ID, API key, secret, etc. using the requireIntegration method.

requireIntegration call definition

The requireIntegration method contains the following two parameters:

• The first parameter is a string or an array of strings containing the destination names.

• The second parameter is a callback that accepts an object containing the names of the destinations that were successfully or unsuccessfully loaded on the page.

An example is shown below:

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rudderanalytics.requireIntegration(
  ["GoogleAnalytics", "Hotjar", "Hubspot"],
  function(object) {
    console.log(JSON.stringify(object));
  }
);

How it works

Once the JavaScript SDK receives a call, e.g. rudderanalytics.requireIntegration("GA"), it automatically fetches the Google Analytics instrumentation code (e.g. GAPlugin.js). This code handles the transformation and mapping logic for the RudderStack event payload and the call type (track, page, etc.) to Google Analytics' corresponding payload and API calls (for e.g. send, set, etc.)

The SDK maintains a call queue and the API calls to it are processed one after the other. The processing of this call queue will be blocked once the requireIntegration method is called.

Use-case

Suppose the user makes a call rudderanalytics.requireIntegration("GA"). All the subsequent calls made to the SDK (such as page, track, alias, group, etc.) will get enqueued until the GAPlugin.js and Google Analytics' analytics.js is loaded on the web page. Once the plugin and the end destination snippet is loaded, the calls in the call queue will be processed, and the corresponding calls to analytics.js will start flowing.

Sample call flow

The following workflow sums up the flow of the event payload when the user calls requireIntegration():

Contact us

For more information or queries on any of the sections covered in this guide, you can contact us or start a conversation in our Slack community.

If you come across any issues while using the JavaScript SDK, feel free to submit them on our GitHub issues page.