v136 · javascript

Startup Timer

Measures the simulated parse + first-call overhead for a heavy initialization function, with and without the //# allFunctionsCalledOnLoad magic comment. The benchmark creates a Blob URL from each version, imports it, and times how long the first call takes — showing when eager compilation pays off.

checking performance.mark…

Normally V8 lazy-compiles functions: the bytecode is generated only on the first call. For functions that are always called at startup, this is wasted work — you pay the compilation cost right when responsiveness matters most. The //# allFunctionsCalledOnLoad magic comment tells V8 to eagerly compile everything in the file, amortising the cost with the initial parse.

Function count (simulated module size): Runs per test:

Without compile hint

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ms median first call

With allFunctionsCalledOnLoad

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ms median first call

Individual runs

Run the benchmark to see results.

What each version looks like

// Click "Run benchmark" to see the generated module snippets.