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Make sure you stay up-to-date with your library versions.
By: Andreas Grabner
Jun. 24, 2011 10:00 AM
The following is a screenshot of the Performance Report analyzing the Boston Bruins Page on msn.foxsports.com using Firefox 3.6. The Performance Report highlights 3 interesting things:
The History on CSS Class Name Lookups
Why is Spry.$$ so slow on Firefox?
Instead of leveraging the native getElementsByClassName method of Firefox the implementation of Spry.$$ uses its own implementation. Using getElementsByTagName with no specific tag name returns ALL DOM Elements – 2787 in total on that page. The library then iterates through all of these DOM elements, reading the className DOM Property and matching it against “prev_label”. Accessing 2787 DOM Properties is a costly operation and takes 170ms in that instance. That’s why Spry.$$ takes that long.
Solve this problem by upgrading your Libraries
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