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Unpacking the Black Box: Benchmarking JS Parsing and Execution on Mobile Devices

Rhinelander South
Average rating: ****.
(4.12, 8 ratings)

Optimizing the experience on mobile devices is a major priority for our industry, but many client performance characteristics are not well understood. In pursuit of the 1000ms time-to-glass holy grail, we wrote a tool to benchmark the initial parse and execute times of our JavaScript files. While high end devices are expectedly fast, midrange and lower end ones are surprisingly slow. We’ll share our full suite of results, the methodology used and some optimization techniques – plus release an open source tool for performing these tests yourself.

Photo of Daniel Espeset

Daniel Espeset


Daniel Espeset is a Senior Software Engineer on the Performance team at Etsy. He enjoys hacking on build processes, improving front-end architecture and pursuing moon-shot experiments in code instrumentation and static analysis. If he were granted three wishes he would ask for all the CDNs to support SPDY (you know who you are), Safari to implement the Navigation Timing API and unlimited future wishes (obv). He lives in Brooklyn with his wife Garity and their two cats, Fannie and Cece.