Reusable docker image for AngularJS - angularjs

Question

We have an AngularJS application. We wrote a dockerfile for it so it's reusable on every system. The dockerfile isn't a best practice and it's maybe some weird build up (build and hosting in same file) for some but it's just created to run our angularjs app locally on each PC of every developer.
Dockerfile:
FROM nginx:1.10
... Steps to install nodejs-legacy + npm
RUN npm install -g gulp
RUN npm install
RUN gulp build
.. steps to move dist folder
We build our image with docker build -t myapp:latest .
Every developer is able to run our app with docker run -d -p 80:80 myapp:latest
But now we're developing other backends. So we have a backend in DEV, a backend in UAT, ...
So there are different URLS which we need to use in /config/xx.json
{
...
"service_base": "https://backend.test.xxx/",
...
}
We don't want to change that URL every time, rebuild the image and start it. We also don't want to declare some URLS (dev, uat, prod, ..) which can be used there. We want to perform our gulp build process with an environment variable instead of a hardcoded URL.
So we we can start our container like this:
docker run -d -p 80:80 --env URL=https://mybackendurl.com app:latest
Is there someone who has experience with this kind of issues? So we'll need an env variable in our json and building it and add the URL later on if that's possible.

Answer 1

EDIT : Better option is to use build args
Instead of passing URL at docker run command, you can use docker build args. It is better to have build related commands to be executed during docker build than docker run.
In your Dockerfile,
ARG URL
And then run
docker build --build-arg URL=<my-url> .
See this stackoverflow question for details

Answer 2

This was my 'solution'. I know it isn't the best docker approach but just for our developers it was a big help.
My dockerfile looks like this:
FROM nginx:1.10
RUN apt-get update && \
apt-get install -y curl
RUN sed -i "s/httpredir.debian.org/`curl -s -D - http://httpredir.debian.org/demo/debian/ | awk '/^Link:/ { print $2 }' | sed -e 's#<http://\(.*\)/debian/>;#\1#g'`/" /etc/apt/sources.list
RUN \
apt-get clean && \
apt-get update && \
apt-get install -y nodejs-legacy && \
apt-get install -y npm
WORKDIR /home/app
COPY . /home/app
RUN npm install -g gulp
RUN npm install
COPY start.sh /
CMD ["./start.sh"]
So after the whole include of the app + npm installation inside my nginx I start my container with the start.sh script.
The content of start.sh:
#!/bin/bash
sed -i 's#my-url#'"$DATA_ACCESS_URL"'#' configs/config.json
gulp build
rm -r /usr/share/nginx/html/
//cp right folders which are created by gulp build to /usr/share/nginx/html
...
//start nginx container
/usr/sbin/nginx -g "daemon off;"
So the build will happen when my container starts. Not the best way of course but it's all for the needs of the developers. Have an easy local frontend.
The sed command will perform a replace on the config file which contains something like:
{
"service_base": "my-url",
}
So my-url will be replaced by my the content of my environment variable which I willd define in my docker run command.
Than I'm able to perform.
docker run -d -p 80:80 -e DATA_ACCESS_URL=https://mybackendurl.com app:latest
And every developer can use the frontend locally and connect with their own backend URL.