Cant Serve statics files using NGINX and Digital Ocean - node.js

Question

/etc/nginx/sites-available/default conf.
Hello, I am using DigialOcean NodeJS one click app set up for my app. NGINX is serving my HTML files, but its not serving my css or java files. I have tried to add location blocks for the public folder which is where my stylesheets and images and java files are. I don't know NGINX very much so any help would be appreciated.
##
# You should look at the following URL's in order to grasp a solid understanding
# of Nginx configuration files in order to fully unleash the power of Nginx.
# https://www.nginx.com/resources/wiki/start/
# https://www.nginx.com/resources/wiki/start/topics/tutorials/config_pitfalls/
# https://wiki.debian.org/Nginx/DirectoryStructure
#
# In most cases, administrators will remove this file from sites-enabled/ and
# leave it as reference inside of sites-available where it will continue to be
# updated by the nginx packaging team.
#
# This file will automatically load configuration files provided by other
# applications, such as Drupal or Wordpress. These applications will be made
# available underneath a path with that package name, such as /drupal8.
#
# Please see /usr/share/doc/nginx-doc/examples/ for more detailed examples.
##
# Default server configuration
server {
listen 80 default_server;
listen [::]:80 default_server;
# SSL configuration
#
# listen 443 ssl default_server;
# listen [::]:443 ssl default_server;
#
# Note: You should disable gzip for SSL traffic.
# See: https://bugs.debian.org/773332
#
# Read up on ssl_ciphers to ensure a secure configuration.
# See: https://bugs.debian.org/765782
#
# Self signed certs generated by the ssl-cert package
# Don't use them in a production server!
#
# include snippets/snakeoil.conf;
root /Portfolio;
# Add index.php to the list if you are using PHP
index index.html index.htm index.nginx-debian.html;
server_name 157.230.203.182;
location ^~ /assets/ {
gzip_static on;
expires 12h;
add_header Cache-Control public;
}
location / {
proxy_http_version 1.1;
proxy_cache_bypass $http_upgrade;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_pass http://localhost:8080;
}
}

Answer 1

I had to add
location ~* \.(css|gif|html|ico|jepg|jpg|mp4||js|jsx|pdf|php|png|scss|svg|txt|zip) {
add_header Cache-Control public;
add_header Cache-Control must-revalidate;
}
It works now but I had to add the above code
not sure why what this code does to be honest. If someone could explain that would be helpful.