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.

Answer 1

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

Answer 2

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).

Answer 3

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

Answer 4

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

Answer 5

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