What Is a JavaScript Action?
A JavaScript action is an action whose entry point is a Node program executed directly by the runner's bundled runtime. It avoids container startup, so it launches quickly and runs on any runner OS that has the runtime. Most fast, cross-platform actions are written this way.
Why it matters
Because it skips a container pull, a JavaScript action is the lowest-latency execution model and the most portable across Linux, Windows, and macOS runners. The trade-off is that it depends on the runner's runtime and must bundle its own dependencies. It is the default choice for lightweight, widely used actions.
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