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Lesson 22 — Health-gated deploy (expert)
Promote only after checks pass
A health-gated deploy starts the new version (green) next to the old one (blue), runs its health check several times, and switches traffic only if every check passes. One failed check means traffic stays on blue. every() returns true only if the test is true for all items.
[true, true, false].every(Boolean) // false
Note: real DevOps tools (CI servers, load balancers, Docker, Kubernetes) cannot run in your browser, so this exercise is a small plain-JS simulation of the logic those tools use.
Why it matters: this gate is what makes "zero-downtime deploy" actually zero-downtime.
In promote(), switch active to "green" only when every check in the list is true.
Run your code — when the output matches the task, you will see a green check. Then mark the lesson complete.
Test your knowledgeA quick 3-question quiz on this lesson — instant feedback.
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