fix(tracker): prevent multiple initialization when script injected more than once #3606
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Greptile Summary
This PR fixes a critical issue where the Umami tracker script could be initialized multiple times when injected repeatedly by modern JavaScript frameworks. The problem occurs when frameworks like TanStack Start re-render the <head> section, causing the same script to execute multiple times and resulting in duplicate pageview and event tracking.
The solution implements a simple but effective global guard mechanism by adding two lines at the very beginning of the tracker's IIFE (Immediately Invoked Function Expression). The fix checks for the existence of window.__umami_tracker_loaded and immediately returns if it's already set, preventing re-initialization. If the flag doesn't exist, it sets it to true and continues with normal execution.
This change integrates seamlessly with the existing tracker architecture without modifying any core functionality. The tracker script (src/tracker/index.js) is designed to be a standalone module that handles all analytics tracking for websites using Umami. By adding the guard at the top level of the IIFE, the fix ensures that all subsequent initialization code (event handlers, data collection, API calls) only runs once, regardless of how many times the script tag is injected into the DOM.
The approach follows established patterns in JavaScript for preventing script re-execution and maintains backward compatibility since it only adds a simple global flag that doesn't interfere with existing functionality.
Confidence score: 5/5
- This PR is extremely safe to merge with virtually no risk of causing issues
- Score reflects a minimal, well-targeted fix that addresses a specific problem without touching core functionality
- No files require special attention as the change is isolated and straightforward
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Couldn't you just check for window.umami? |
checking window.umami is indeed more straightforward actually. if two async scripts are loaded at the same time, there is a possibility where both script could pass |
Issue #3596
Problem
When the Umami tracker script is injected more than once (e.g. by frameworks that
re-render , such as TanStack Start), the tracker is initialized multiple times,
causing duplicate pageview/event tracking
Solution
Add a global guard (
window.__umami_tracker_loaded) at the top of the tracker script