Can uglify-js remove the console.log statements?

Question

I'm using uglify-js to minify the source code. I want to remove the console.log statements of the original source code. Is it possible? Or is there any other compressor tool supports this?

I use the code as below in Node.js.

var uglify = require('uglify-js');
var originalSourceCode = 'var name = function(){var str = "test"; return str}; console.log("log data");';
var minifiedCode = uglify.minify(originalSourceCode, {
                fromString : true,
                mangle: {},
                warnings: true
            });
console.log(minifiedCode);

The output is:

$node m.js
{ code: 'var name=function(){var a="test";return a};console.log("log data");',
  map: 'null' }

In the minified code the console.log isn't removed.

I think there are several Grunt-plugins which can do that. – hgoebl Nov 20 '13 at 10:21 — hgoebl, Nov 20 '13 at 10:21

Joshua · Answer 1 · 2014-02-06T14:06:08.293

80

There's also another option called drop_console which has been added recently (late 2013)

drop_console -- default false. Pass true to discard calls to console.* functions

This is added to the grunt init config like this:

grunt.initConfig({
  uglify: {
    options: {
      compress: {
        drop_console: true // <-
      }
    },
    my_target: {
      files: {
        'dest/output.min.js': ['src/input.js']
      }
    }
  }
});

As taken from the grunt-contrib-uglify github documents

edited Feb 06 '14 at 14:06

answered Jan 09 '14 at 12:29

Joshua

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1

That is awesome, but could you improve your answer by being more precise on where to add this in the Gruntfile.js? – Micros Jan 09 '14 at 16:08
2

See https://github.com/gruntjs/grunt-contrib-uglify/blob/master/docs/uglify-examples.md add it to the compress parameter – geographika Jan 17 '14 at 16:49
1

Has now changed to dropConsole in camel case – benpalmer May 15 '14 at 09:25
This is not working!!! It says drop_console / dropConsole is not supported @benpalmer – Captain Obvious Jun 16 '14 at 14:16
Agreed, i get `Identifier 'drop_console' is not in camel case.` and an error if you make it `dropConsole` – benpalmer Jun 19 '14 at 16:31
I also tried it both ways, doesn't seem to work anymore. – Kris Hollenbeck Jun 19 '14 at 20:28
2

Works within grunt-require as well: `requirejs: { options: { uglify2: { compress: { drop_console: true } } } }` – ericsoco Jun 23 '14 at 06:13

score 29 · Accepted Answer · answered Nov 21 '13 at 09:48

In the lastest uglify-js ( v2.4.3), a new compress option ‘pure_funcs’ is added. If I add the console.log functions to this array, it will be removed in the minified js file. The test code below shows how this option works. This is exactly what I want.

// file: m.js
var uglify = require('uglify-js');
var originalSourceCode = 'var name = function(){var str = "test"; return str}; console.log("log data" + name());';
var minifiedCode = uglify.minify(originalSourceCode, {
                fromString : true,
                mangle: {},
                warnings: true,
                compress:{
                    pure_funcs: [ 'console.log' ]
                }
            });
console.log(minifiedCode);

$node m.js
WARN: Dropping side-effect-free statement [?:1,53]
{ code: 'var name=function(){var n="test";return n};',
  map: 'null' }

Quotes from https://github.com/mishoo/UglifyJS2

pure_funcs -- default null. You can pass an array of names and UglifyJS will assume that those functions do not produce side effects. DANGER: will not check if the name is redefined in scope. An example case here, for instance var q = Math.floor(a/b). If variable q is not used elsewhere, UglifyJS will drop it, but will still keep the Math.floor(a/b), not knowing what it does. You can pass pure_funcs: [ 'Math.floor' ] to let it know that this function won't produce any side effect, in which case the whole statement would get discarded. The current implementation adds some overhead (compression will be slower).

score 4 · Answer 3 · answered Nov 20 '13 at 09:54

4

You can use Groundskeeper to do this though it will be a separate step.

answered Nov 20 '13 at 09:54

Karl-Johan Sjögren

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score 4 · Answer 4 · answered Jan 07 '17 at 12:31

4

for -c option, set drop_console to be true: uglifyjs app.js -m -c drop_console=true -o app.min.js

answered Jan 07 '17 at 12:31

KiwenLau

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How to add in Grunt.js ? – Sivaprabu Ganesan May 21 '17 at 09:43

score 1 · Answer 5 · answered Oct 13 '17 at 11:47

1

If you are using gulp, use 'gulp-strip-debug' to remove console, alert and debugger. https://www.npmjs.com/package/gulp-strip-debug

answered Oct 13 '17 at 11:47

pratik nagariya

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Can uglify-js remove the console.log statements?

5 Answers5

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