Strategy for deploying/hosting javascript-based static websites in containers
From my standpoint the best approach would be to:


Separate build process using Jenkins that would build NodeJS project into distribution and wrap it into Docker image
Spin up Docker registry that would accumulate Docker images from Jenkins (this registry should be accessible from Kubernetes cluster)
Move environment variables to Jenkins secrets or use separate tool to collect and combine configurations from external Git repo (we use Spring Cloud Config through REST API to collect json/yml definitions for every application in every environment)


Using Jenkins you can configure continuous delivery system based on generic Pipelines. Possible flow would be:


Developers finish their work in correspondence to GitFlow (latest Pull Request merged into Release branch)
Webhook triggers Jenkins pipeline:


Stage 1: collect environment definition
Stage 2: build NodeJS app using npm
Stage 3: build Nginx Docker image with distribution
Stage 4: push Docker image to Docker registry
Stage 5: deploy/update service in Kubernetes using standard definitions

Notifications send in regard of results


This process might be visualized using Rancher. I can answer your questions in chat.