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How SpiderMonkey, Firefox's JavaScript Engine, Compiles and Collects Garbage

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SpiderMonkey is the JavaScript engine inside Firefox, responsible for parsing, compiling, and running JavaScript code. It descends from the original Netscape engine created by Brendan Eich and has been developed continuously since the mid-1990s. The engine uses multiple tiers, running cold code in an interpreter and upgrading frequently executed code through baseline and optimizing JIT compilers. When type assumptions made by the JIT are violated, it triggers costly deoptimizations, which developers can spot in the Firefox Profiler. Memory is managed by a generational, incremental, and compacting garbage collector, and the article notes that SpiderMonkey and Chrome's V8 engine are broadly comparable in performance.

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How SpiderMonkey, Firefox's JavaScript Engine, Compiles and Collects Garbage · ShortSingh