Command line uglify-js

Recently I was working on a small project where I wanted to get some jquery-like functionality in an javascript application but I wanted to keep the downloads as slim as possible. I used zepto.js for the query features: the minified copy of zepto is about 1/4 the size of recent versions of jquery 1.x. But zepto is split into a number of modules, some of which aren’t necessarily included in the default zepto distributions (things like ajax and effects aren’t in the core distribution of Zepto). So I needed to concat together several modules of zepto.js and minify/uglify the code to reduce its size. Didn’t want to take the time to create a package.json and a Gruntfile to do the building; just wanted to download zepto and walk away with a minified copy of the code that I needed.

Many npm packages come with support for command line execution, and uglify-js is one of them. I found that npm will install requested packages without having a package.json file present – it’ll complain a little bit, but it will do it:

$ npm install zepto uglify-js
|-+ uglify-js@3.0.27 
│ |-- commander@2.11.0 
│ |-- source-map@0.5.6 
|-- zepto@1.2.0 
npm WARN ENOENT ENOENT: no such file or directory, open '/Users/curious1/prog/javascript/zepto/package.json'
npm WARN EPACKAGEJSON /Users/curious1/prog/javascript/zepto No description
npm WARN EPACKAGEJSON /Users/curious1/prog/javascript/zepto No repository field.
npm WARN EPACKAGEJSON /Users/curious1/prog/javascript/zepto No README data
npm WARN EPACKAGEJSON /Users/curious1/prog/javascript/zepto No license field.

Without doing a ‘npm init’ to create a package.json file, npm created the usual “node_modules” directory with the requested packages (as well as the ones those packages are dependent on):

$ ls node_modules
commander/    source-map/     uglify-js/    zepto/

The Zepto package comes with the default minified and unminified versions in the dist/ directory, and the extra (and unminified) modules in the src/ directory:

$ ls node_modules/zepto
MIT-LICENSE    dist/    package.json    src/
$ ls node_modules/zepto/dist
zepto.js    zepto.min.js
$ ls node_modules/zepto/src
ajax.js        deferred.js    fx.js           ios3.js        zepto.js
assets.js      detect.js      fx_methods.js   selector.js
callbacks.js   event.js       gesture.js      stack.js
data.js        form.js        ie.js           touch.js

The uglify-js module came with an executable Node command line script in the typical bin/ directory:

$ ls node_modules/uglify-js/bin
$ ls -l node_modules/uglify-js/bin/uglifyjs
-rwxr-xr-x  1 curious1  staff  14325 Jul 29 14:44 node_modules/uglify-js/bin/uglifyjs*
$ file node_modules/uglify-js/bin/uglifyjs
node_modules/uglify-js/bin/uglifyjs: a node script text executable
$ head node_modules/uglify-js/bin/uglifyjs

(it’s worth noting at this point that I have the ‘ls’ command aliased to ‘ls -CF’ in my bash shell: this causes “*” to be printed after executable files and a “/” after directories)

The help message for the ‘uglifyjs’ command lists the options that I need:

$ node_modules/.bin/uglifyjs --help
  Usage: uglifyjs [options] [files...]
    -V, --version                output the version number
    -p, --parse        Specify parser options.
    -c, --compress [options]     Enable compressor/specify compressor options.
    -m, --mangle [options]       Mangle names/specify mangler options.
...more output...

I used curly brace syntax to select the zepto module files that I want under the “src/” directory:

$ uglifyjs node_modules/zepto/src/{zepto,event,ajax,form,ie,fx,fx_methods,detect,touch,gesture,ios3}.js \
    -m -c -p 1 --source-map > zepto.x.min.js output..

The result: a concat’ed and minified zepto.js (named “zepto.x.min.js” for “eXtended”):

$ ls -l zepto.x.min.js
-rw-r--r--  1 curious1  staff  34564 Aug  8 15:22 zepto.x.min.js

The resulting minified .js file is slightly bigger than the one that comes in the default distribution, but it includes the features like ajax support, event handling, easing effects that I need and that aren’t in the default distribution.

Just taking a peak inside the minified code: uglification removes a lot of newlines, so the final file contains just a very few long lines. I used ‘cut -c1-200’ to show just the first 200 characters of each line:

$ cut -c 1-200 zepto.x.min.js
var Zepto=function(){function t(t){return null==t?String(t):W[]||"object"}function e(e){return"function"==t(e)}function n(t){return null!=t&&t==t.window}function i(t){return null!=t&&t.nodeTy
e&&(h.el.trigger("swipe"),h.el.trigger("swipe"+e))}).on("touchstart MSPointerDown pointerdown",function(e){(v=a(e,"down"))&&!o(e)||(g=v?e:e.touches[0],e.touches&&1===e.touches.length&&h.x2&&(h.x2=void

npm packages typically come with other things like a LICENSE file and a (“markdown”) file:

$ ls node_modules/uglify-js/
LICENSE    bin/    lib/    package.json    tools/

It’s often worth skimming the files that come with npm packages: they often provides valuable documentation and examples on how to use a tool.

For larger development projects and/or projects involving multiple contributors, a more structured project might be necessary (package.json, grunt or gulp to automate the copy/concat/uglify process). But for simple projects (or just some exploration and experimentation) it’s useful to have the command line tools available!


Set up a project quickly to experiment with npm Javascript packages (no npm init):

$ npm install zepto uglify-js

Found executable forms of the code package under the “bin/” directory:

$ ls node_modules/uglify-js/bin

Using some standard Linux tools to learn about the runnable code:

$ ls -l node_modules/uglify-js/bin/uglifyjs
$ file node_modules/uglify-js/bin/uglifyjs
$ head node_modules/uglify-js/bin/uglifyjs

Checking command line options for ‘uglifyjs’ with “–help” (a “help” arg may also work depending on the package):

$ node_modules/uglify-js/bin/uglifyjs --help

The zepto source modules were under a “src/” subdirectory:

$ ls node_modules/uglify-js/src

Invoking ‘uglifyjs’ to build and minify the custom js file:

$ uglifyjs node_modules/zepto/src/{zepto,event,ajax,form,ie,fx,fx_methods,detect,touch,gesture,ios3}.js \
    -m -c -p 1 --source-map > zepto.x.min.js output..

Examining the minified/uglified .js file:

$ cut -c 1-200 zepto.x.min.js


npm: “the package manager for JavaScript”

uglifyjs: “a JavaScript parser, minifier, compressor or beautifier toolkit”

zeptojs: “the aerogel-weight jQuery-compatible JavaScript library”


$ npm -version
$ node –version
$ npm list –depth 0
|– uglify-js@3.0.27
|– zepto@1.2.0

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