This is a summary of popular methods for incorporating the "Build once, deploy everywhere" principal of DevOps when delivering any type of server based application. The main idea is to use the same bundle for all environments, from testing to production. This approach enables easy deployment and testability and is considered a fundamental principle of continuous delivery. Supporting resources are included below and will be referenced where possible.
In static web applications, the configuration is baked in at build time, meaning you most likely need to create individual build artifacts for dev, test, uat, live etc. This can turn into a significant time sink if the build process is even remotely lengthy.