Docker app won`t work but application works if not in docker

  docker, dockerfile, node.js, reactjs

I have built a react and node app and it works. I am trying to build an docker image and run it it compiles but when i try to access it thru thr browser it says This site can’t be reachedlocalhost refused to connect. This is the dockerfile that i`ve written because I think this is the problem:

# pull official base image
FROM node:13.12.0-alpine

# set working directory
WORKDIR /client

# add `/app/node_modules/.bin` to $PATH
ENV PATH /client/node_modules/.bin:$PATH

# install app dependencies
COPY package.json ./
COPY package-lock.json ./
RUN npm install --silent
RUN npm install [email protected] -g --silent

# add app
COPY . ./

# start app
CMD ["npm", "start"]

FROM node:12

# Create app directory

# Install app dependencies
# A wildcard is used to ensure both package.json AND package-lock.json are copied
# where available ([email protected]+)
COPY package*.json ./

RUN npm install
# If you are building your code for production
# RUN npm ci --only=production

# Bundle app source
COPY . .

CMD [ "node", "index.js" ]

Source: Docker Questions