replace uglifier gem by terser to minimize javascript files

The minimization of JavaScript files is useful, because LinuxFr.org
includes jQuery and jQeury UI and certainly don't use all the tools
provided by them.

The decaffeinate process to build JavaScript files from old
coffee script files has built EcmaScript 6 files.

As uglifier is not compatible with EcmaScript 6, it has been replaced by terser
which is recommended by the uglifier project itself.

Author: Trim

Gemfile

@@ -41,7 +41,7 @@ assets = true if ENV['RAILS_GROUPS'] == "assets"
 gem "jquery-rails",          "~>4.0", require: assets
 gem "normalize-rails",       "~>8.0", require: assets
 gem "sass-rails",            "~>5.0", require: assets
-gem "uglifier",                       require: assets
+gem "terser", "~> 1.2",               require: assets
 
 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console

Gemfile.lock

@@ -359,13 +359,13 @@ GEM
       state_machines-activemodel (>= 0.9.0)
     stringio (3.1.0)
     temple (0.10.3)
+    terser (1.2.0)
+      execjs (>= 0.3.0, < 3)
     thor (1.3.1)
     tilt (2.3.0)
     timeout (0.4.1)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
-    uglifier (4.2.0)
-      execjs (>= 0.3.0, < 3)
     unicorn (6.1.0)
       kgio (~> 2.6)
       raindrops (~> 0.7)
@@ -426,7 +426,7 @@ DEPENDENCIES
   sitemap_generator (~> 2.1)
   spring
   state_machines-activerecord
-  uglifier
+  terser (~> 1.2)
   unicorn (~> 6.1)
   web-console
 

config/environments/alpha.rb

@@ -21,7 +21,7 @@
   config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES'].present?
 
   # Compress JavaScripts and CSS.
-  config.assets.js_compressor = :uglifier
+  config.assets.js_compressor = :terser
   config.assets.css_compressor = :sass
 
   # Do not fallback to assets pipeline if a precompiled asset is missed.

config/environments/production.rb

@@ -26,7 +26,7 @@
   config.public_file_server.enabled = ENV["RAILS_SERVE_STATIC_FILES"].present?
 
   # Compress CSS using a preprocessor.
-  config.assets.js_compressor = :uglifier
+  config.assets.js_compressor = :terser
   config.assets.css_compressor = :sass
 
   # Do not fallback to assets pipeline if a precompiled asset is missed.