RewriteEngine on
RewriteBase /

# do not do anything for already existing files
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule (.*) - [L]

# if request is no valid file NOR directory
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
# if static asset do not do anything
RewriteRule (.*)(css|js|html|png|jpe?g|gif|bmp|ico|json|csv|otf|eot|svg|svgz|ttf|woff|woff2|ijmap|pdf|tif|map) - [NC,L,R=404]
# everything else should be redirected to /index.html so it can be routed by it
RewriteRule (.*) /index.html [L]