remove console.log on assets precompile
Question
During assets:precompile the javascript is minified, but console.logs are left in.
is there a way to remove all console.logs on precompile when the code is pushed to production?
4 answers
solution1
23 ACCPTED 2014-01-23 16:02:28
As of Uglifier 2.4.0 the :compress option includes support for :drop_console which means you can easily remove all console.* functions using something like this in your config/environments/production.rb file:
# Compress JavaScripts
config.assets.compress = true
config.assets.js_compressor = Uglifier.new(
# Remove all console.* functions
:compress => { :drop_console => true }
) if defined? Uglifier
solution2
5 2013-03-16 05:28:39
You could add this to application.js.erb . This solution would prevent any logging to console.log() in production environment, period. But it will still allow logging to console.error() .
<% if Rails.env.production? %>
window.console = {};
window.console.log = function(){};
<% else %>
// the || in the code ensures IE compatability
window.console = window.console || {};
window.console.log = window.console.log || function(){};
<% end %>
solution3
2 2012-08-01 18:24:22
To point you in the right direction, check out the Use as a code pre-processor section of UglifyJS .
I need to research more about how to pass a --define DEVMODE=false flag within the rake assets:precompile , but adjusting your code to wrap console.log in with the DEVMODE boolean as described in the link above should get you the result you're looking for.
Update:
In some file that will load during rake assets:precompile , add the following monkey patch.
class Uglifier
private
def mangle_options
{
"mangle" => @options[:mangle],
"toplevel" => @options[:toplevel],
"defines" => { DEVMODE: ["name", "null"] }, # This line sets DEVMODE
"except" => @options[:except],
"no_functions" => @options[:mangle] == :vars
}
end
end
As I mentioned in a comment below, Uglifier does not support passing a :defines mangle option . You could optionally change the marked line above to "defines" => @options[:defines] and update your config with this line
config.assets.js_compressor = Uglifier.new(defines: { DEVMODE: ["name", "null"] })
When running the rake task, DEVMODE will now be converted to null in your source. Now, given the following code in your Javascript source:
if (typeof DEVMODE === 'undefined') {
DEVMODE = true;
}
if (DEVMODE) {
console.log('some log message');
}
By default (in development mode) , DEVMODE will be set to true , causing the console.log() to execute. When rake assets:precompile is run, UglifyJS is going to set DEVMODE to null before compilation/compression begins. When walking over if (null) { it will see that the condition will never evaluate true , and will strip this dead code from the resulting source.
As long as you write your console.log() calls like above or shorthand as
DEVMODE && console.log('some log message');
the console.log() calls will be stripped from the production code. I can see other benefits to this too outside of stripping console.log() , allowing for other development-specific code to coexist with other Javascript in development mode and only development mode.
solution4
2 2013-03-05 17:32:17
I'd like to mention the solution of bitcrowd . Their idea basically is:
- define a
dataattribute in your body tag that represents the state of your app (development/production/...) - eg<body data-env="<%= Rails.env %>"> depending on this let
console.log()print something out or do nothing at all - eg:if ($('body').data('env') == 'production' || typeof console == "undefined"){ var console = { log: function() {}, debug: function() {}, info: function() {} }; }
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