What’s multi-stage build

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say we have a web app that’s built by npm run build
- that means we need npm in the build process
- we need npm in the Dockerfile (i.e., npm in the image)
and we wanna have a reverse proxy for it
- that means we need nginx in the final image
but when we ship the product, we just need the artifacts built by npm, we don’t need npm itself in our image
that’s where multi-stage build comes it
- it allows us to:
- build at a stage, and only bring the artifacts of the stage to another stage
- leaving all the tools behind
- so that the final image will not contain the unnecessary tools in production environment
  - the final image will be lightweight