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changelog: User-Facing Improvements, Performance, Use defer for non-critical scripts
mitchellhenke
approved these changes
Aug 16, 2024
zachmargolis
approved these changes
Aug 16, 2024
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🛠 Summary of changes
Updates non-critical scripts to use
deferinstead ofasync.While both
asyncanddeferload scripts without blocking the parser,asyncwill block the parser to execute the script as soon as it's loaded, which may block parsing if it happens before parsing is complete.deferwill instead wait for parsing to complete before executing the script, which is acceptable behavior for the scripts affected by the changes in this pull request.The HTML specification includes helpful diagrams illustrating the difference:
Related resource: https://web.dev/articles/optimizing-content-efficiency-loading-third-party-javascript#async-defer
While this resource includes analytics scripts as an example of
asyncusage, it does so under the premise that these are "important for the script to run earlier in the loading process". It's not clear to me that it's important for these to run early.📜 Testing Plan
Verify there is no regression in the loading of scripts marked as
defer, particularlytrack-errors.json http://localhost:3000 should load successfully in default development environments.