Building webpack for production - minified dependencies

Question

Say there is a module on npm called "awesomepackage". I can register it as a dependency of my application via package.json like so:

npm i --save awesomepackage

Inspecting my node_modules folder I see a folder named "awesomepackage" which looks like this:

- index.js
- package.json
- README.md
- lib/
    - awesomepackage.min.js

and I can use the package inside my own application like so:

import {AwesomeThing} from 'awesomepackage';

My question:

When I build my application using webpack my final bundle.js always contains the source code from node_modules/awesomepackage/index.js - regardless of any environment variables I have setup (eg NODE_ENV=production).

Is there any way to tell webpack to use the pre-built files (eg node_modules/awesomepackage/lib/awesomepackage.min.js) if they are shipped as part of an NPM package, instead of re-building from the source?

I have seen solutions that use resolve.alias and noParse in the webpack config with hardcoded paths to minified source files, but doesn't that mostly defeat the purpose of using npm and webpack? I don't want to have to hard-code and maintain paths to every dependency's minified build files!

I got here because my bundle.js jumped 2.5mb when I added moment.js - which is 167kb minified, including all locales, but of which the source code includes 2mb of tests.

Edit

Clearly there is more to it than just minifying the final bundle.js file at the end. For example: why would anybody want to include hundreds of unnecessary unit tests for dependencies in final production code? They don't. Which is why most libraries provide a dist (or similar) folder as part of their npm module.

Answer 1

Let's consider your moment package.

You can always use

import moment from 'node_modules/moment/min/moment-with-locales.min.js'

But it's not a good idea.

---

You shouldn't use minified files in webpack

If you use

import moment from 'moment';

it will build module from source. But if you have minification process in webpack config file it shouldn't be much bigger than shipped .min.js files. Often your own build can be even smaller than original .min.js!

---

Experiment for moment

I measure additional size of my bundle.js after adding moment and its 190 kB and original moment/min/moment-with-locales.min.js size is 207 kB. Your 2.5 MB is probably that you add maps (in my configuration with maps moment weights 2.7 MB) You can analyze that it is build with all locales - webpack can print this statistics (sizes are before minification):

 [373] ./~/moment/moment.js 135 kB {0} [built]
 [374] ./~/moment/locale/af.js 2.62 kB {0} [optional] [built]
 [375] ./~/moment/locale/ar-ma.js 2.12 kB {0} [optional] [built]
 [376] ./~/moment/locale/ar-sa.js 3.16 kB {0} [optional] [built]
 [377] ./~/moment/locale/ar-tn.js 1.97 kB {0} [optional] [built]
 [378] ./~/moment/locale/ar.js 4.59 kB {0} [optional] [built]
 [379] ./~/moment/locale/az.js 3.35 kB {0} [optional] [built]
 [380] ./~/moment/locale/be.js 4.86 kB {0} [optional] [built]
 [381] ./~/moment/locale/bg.js 3.1 kB {0} [optional] [built]
 [382] ./~/moment/locale/bn.js 3.62 kB {0} [optional] [built]
 [383] ./~/moment/locale/bo.js 3.87 kB {0} [optional] [built]
 [384] ./~/moment/locale/br.js 3.44 kB {0} [optional] [built]
 [385] ./~/moment/locale/bs.js 4.7 kB {0} [optional] [built]
 [386] ./~/moment/locale/ca.js 2.97 kB {0} [optional] [built]
 [387] ./~/moment/locale/cs.js 6.4 kB {0} [optional] [built]
 [388] ./~/moment/locale/cv.js 2.33 kB {0} [optional] [built]
 [389] ./~/moment/locale/cy.js 2.92 kB {0} [optional] [built]
 [390] ./~/moment/locale/da.js 2.07 kB {0} [optional] [built]
 [391] ./~/moment/locale/de-at.js 3.03 kB {0} [optional] [built]
 [392] ./~/moment/locale/de.js 2.95 kB {0} [optional] [built]
 [393] ./~/moment/locale/dv.js 2.69 kB {0} [optional] [built]
 [394] ./~/moment/locale/el.js 3.73 kB {0} [optional] [built]
 [395] ./~/moment/locale/en-au.js 2.32 kB {0} [optional] [built]
 [396] ./~/moment/locale/en-ca.js 2.2 kB {0} [optional] [built]
 [397] ./~/moment/locale/en-gb.js 2.38 kB {0} [optional] [built]
 [398] ./~/moment/locale/en-ie.js 2.37 kB {0} [optional] [built]
 [399] ./~/moment/locale/en-nz.js 2.32 kB {0} [optional] [built]
 [400] ./~/moment/locale/eo.js 2.67 kB {0} [optional] [built]
 [401] ./~/moment/locale/es.js 2.97 kB {0} [optional] [built]
 [402] ./~/moment/locale/et.js 3.14 kB {0} [optional] [built]
 [403] ./~/moment/locale/eu.js 2.39 kB {0} [optional] [built]
 [404] ./~/moment/locale/fa.js 3.27 kB {0} [optional] [built]
 [405] ./~/moment/locale/fi.js 3.86 kB {0} [optional] [built]
 [406] ./~/moment/locale/fo.js 2.1 kB {0} [optional] [built]
 [407] ./~/moment/locale/fr-ca.js 2.09 kB {0} [optional] [built]
 [408] ./~/moment/locale/fr-ch.js 2.25 kB {0} [optional] [built]
 [409] ./~/moment/locale/fr.js 2.24 kB {0} [optional] [built]
 [410] ./~/moment/locale/fy.js 2.64 kB {0} [optional] [built]
 [411] ./~/moment/locale/gd.js 2.63 kB {0} [optional] [built]
 [412] ./~/moment/locale/gl.js 2.77 kB {0} [optional] [built]
 [413] ./~/moment/locale/he.js 3.41 kB {0} [optional] [built]
 [414] ./~/moment/locale/hi.js 3.88 kB {0} [optional] [built]
 [415] ./~/moment/locale/hr.js 4.83 kB {0} [optional] [built]
 [416] ./~/moment/locale/hu.js 4 kB {0} [optional] [built]
 [417] ./~/moment/locale/hy-am.js 3.22 kB {0} [optional] [built]
 [418] ./~/moment/locale/id.js 2.94 kB {0} [optional] [built]
 [419] ./~/moment/locale/is.js 4.43 kB {0} [optional] [built]
 [420] ./~/moment/locale/it.js 2.46 kB {0} [optional] [built]
 [421] ./~/moment/locale/ja.js 2.21 kB {0} [optional] [built]
 [422] ./~/moment/locale/jv.js 2.94 kB {0} [optional] [built]
 [423] ./~/moment/locale/ka.js 3.15 kB {0} [optional] [built]
 [424] ./~/moment/locale/kk.js 2.68 kB {0} [optional] [built]
 [425] ./~/moment/locale/km.js 2.02 kB {0} [optional] [built]
 [426] ./~/moment/locale/ko.js 2 kB {0} [optional] [built]
 [427] ./~/moment/locale/ky.js 2.69 kB {0} [optional] [built]
 [428] ./~/moment/locale/lb.js 4.92 kB {0} [optional] [built]
 [429] ./~/moment/locale/lo.js 2.32 kB {0} [optional] [built]
 [430] ./~/moment/locale/lt.js 4.37 kB {0} [optional] [built]
 [431] ./~/moment/locale/lv.js 3.9 kB {0} [optional] [built]
 [432] ./~/moment/locale/me.js 4.1 kB {0} [optional] [built]
 [433] ./~/moment/locale/mk.js 3.11 kB {0} [optional] [built]
 [434] ./~/moment/locale/ml.js 2.81 kB {0} [optional] [built]
 [435] ./~/moment/locale/mr.js 5.39 kB {0} [optional] [built]
 [436] ./~/moment/locale/ms-my.js 2.86 kB {0} [optional] [built]
 [437] ./~/moment/locale/ms.js 2.85 kB {0} [optional] [built]
 [438] ./~/moment/locale/my.js 2.73 kB {0} [optional] [built]
 [439] ./~/moment/locale/nb.js 2.23 kB {0} [optional] [built]
 [440] ./~/moment/locale/ne.js 3.81 kB {0} [optional] [built]
 [441] ./~/moment/locale/nl.js 2.63 kB {0} [optional] [built]
 [442] ./~/moment/locale/nn.js 2.09 kB {0} [optional] [built]
 [443] ./~/moment/locale/pa-in.js 4.01 kB {0} [optional] [built]
 [444] ./~/moment/locale/pl.js 3.94 kB {0} [optional] [built]
 [445] ./~/moment/locale/pt-br.js 2.23 kB {0} [optional] [built]
 [446] ./~/moment/locale/pt.js 2.34 kB {0} [optional] [built]
 [447] ./~/moment/locale/ro.js 2.61 kB {0} [optional] [built]
 [448] ./~/moment/locale/ru.js 7.08 kB {0} [optional] [built]
 [449] ./~/moment/locale/se.js 2.23 kB {0} [optional] [built]
 [450] ./~/moment/locale/si.js 2.43 kB {0} [optional] [built]
 [451] ./~/moment/locale/sk.js 5.49 kB {0} [optional] [built]
 [452] ./~/moment/locale/sl.js 6.16 kB {0} [optional] [built]
 [453] ./~/moment/locale/sq.js 2.45 kB {0} [optional] [built]
 [454] ./~/moment/locale/sr-cyrl.js 4.1 kB {0} [optional] [built]
 [455] ./~/moment/locale/sr.js 4.09 kB {0} [optional] [built]
 [456] ./~/moment/locale/ss.js 3.12 kB {0} [optional] [built]
 [457] ./~/moment/locale/sv.js 2.4 kB {0} [optional] [built]
 [458] ./~/moment/locale/sw.js 2.08 kB {0} [optional] [built]
 [459] ./~/moment/locale/ta.js 4.21 kB {0} [optional] [built]
 [460] ./~/moment/locale/te.js 3.09 kB {0} [optional] [built]
 [461] ./~/moment/locale/th.js 2.4 kB {0} [optional] [built]
 [462] ./~/moment/locale/tl-ph.js 2.14 kB {0} [optional] [built]
 [463] ./~/moment/locale/tlh.js 4.09 kB {0} [optional] [built]
 [464] ./~/moment/locale/tr.js 2.9 kB {0} [optional] [built]
 [465] ./~/moment/locale/tzl.js 3.59 kB {0} [optional] [built]
 [466] ./~/moment/locale/tzm-latn.js 2.11 kB {0} [optional] [built]
 [467] ./~/moment/locale/tzm.js 2.06 kB {0} [optional] [built]
 [468] ./~/moment/locale/uk.js 5.4 kB {0} [optional] [built]
 [469] ./~/moment/locale/uz.js 2.03 kB {0} [optional] [built]
 [470] ./~/moment/locale/vi.js 2.71 kB {0} [optional] [built]
 [471] ./~/moment/locale/x-pseudo.js 2.5 kB {0} [optional] [built]
 [472] ./~/moment/locale/zh-cn.js 4.35 kB {0} [optional] [built]
 [473] ./~/moment/locale/zh-tw.js 3.12 kB {0} [optional] [built]
 [474] ./~/moment/locale ^\.\/.*$ 2.41 kB {0} [optional] [built]

So why your custom build is smaller? You can use more aggressive minification. My build give me this information (probably it loose some weight at this point):

Condition always true [./~/moment/moment.js:8,0]
Condition always true [./~/moment/locale/af.js:6,0]
Condition always true [./~/moment/locale/ar-ma.js:7,0]
Condition always true [./~/moment/locale/ar-sa.js:6,0]
Condition always true [./~/moment/locale/ar-tn.js:5,0]
Condition always true [./~/moment/locale/ar.js:8,0]
Condition always true [./~/moment/locale/az.js:6,0]
Condition always true [./~/moment/locale/be.js:8,0]
Condition always true [./~/moment/locale/bg.js:6,0]
Condition always true [./~/moment/locale/bn.js:6,0]
Condition always true [./~/moment/locale/bo.js:6,0]
Condition always true [./~/moment/locale/br.js:6,0]
Condition always true [./~/moment/locale/bs.js:7,0]
Condition always true [./~/moment/locale/ca.js:6,0]
Condition always true [./~/moment/locale/cs.js:6,0]
Dropping unreachable code [./~/moment/locale/cs.js:31,0]
Dropping unreachable code [./~/moment/locale/cs.js:40,0]
Dropping unreachable code [./~/moment/locale/cs.js:49,0]
Dropping unreachable code [./~/moment/locale/cs.js:58,0]
Dropping unreachable code [./~/moment/locale/cs.js:67,0]
Condition always true [./~/moment/locale/cv.js:6,0]
Condition always true [./~/moment/locale/cy.js:6,0]
Condition always true [./~/moment/locale/da.js:6,0]
Condition always true [./~/moment/locale/de-at.js:9,0]
Condition always true [./~/moment/locale/de.js:8,0]
Condition always true [./~/moment/locale/dv.js:6,0]
Condition always true [./~/moment/locale/el.js:6,0]
Condition always true [./~/moment/locale/en-au.js:5,0]
Condition always true [./~/moment/locale/en-ca.js:6,0]
Condition always true [./~/moment/locale/en-gb.js:6,0]
Condition always true [./~/moment/locale/en-ie.js:6,0]
Condition always true [./~/moment/locale/en-nz.js:5,0]
Condition always true [./~/moment/locale/eo.js:8,0]
Condition always true [./~/moment/locale/es.js:6,0]
Condition always true [./~/moment/locale/et.js:7,0]
Condition always true [./~/moment/locale/eu.js:6,0]
Condition always true [./~/moment/locale/fa.js:6,0]
Condition always true [./~/moment/locale/fi.js:6,0]
Condition always true [./~/moment/locale/fo.js:6,0]
Condition always true [./~/moment/locale/fr-ca.js:6,0]
Condition always true [./~/moment/locale/fr-ch.js:6,0]
Condition always true [./~/moment/locale/fr.js:6,0]
Condition always true [./~/moment/locale/fy.js:6,0]
Condition always true [./~/moment/locale/gd.js:6,0]
Condition always true [./~/moment/locale/gl.js:6,0]
Condition always true [./~/moment/locale/he.js:8,0]
Condition always true [./~/moment/locale/hi.js:6,0]
Condition always true [./~/moment/locale/hr.js:6,0]
Condition always true [./~/moment/locale/hu.js:6,0]
Dropping unused variable suffix [./~/moment/locale/hu.js:16,0]
Condition always true [./~/moment/locale/hy-am.js:6,0]
Condition always true [./~/moment/locale/id.js:7,0]
Condition always true [./~/moment/locale/is.js:6,0]
Condition always true [./~/moment/locale/it.js:7,0]
Condition always true [./~/moment/locale/ja.js:6,0]
Condition always true [./~/moment/locale/jv.js:7,0]
Condition always true [./~/moment/locale/ka.js:6,0]
Condition always true [./~/moment/locale/kk.js:6,0]
Condition always true [./~/moment/locale/km.js:6,0]
Condition always true [./~/moment/locale/ko.js:10,0]
Condition always true [./~/moment/locale/ky.js:6,0]
Condition always true [./~/moment/locale/lb.js:6,0]
Condition always true [./~/moment/locale/lo.js:6,0]
Condition always true [./~/moment/locale/lt.js:6,0]
Condition always true [./~/moment/locale/lv.js:7,0]
Condition always true [./~/moment/locale/me.js:6,0]
Condition always true [./~/moment/locale/mk.js:6,0]
Condition always true [./~/moment/locale/ml.js:6,0]
Condition always true [./~/moment/locale/mr.js:7,0]
Condition always true [./~/moment/locale/ms-my.js:6,0]
Condition always true [./~/moment/locale/ms.js:6,0]
Condition always true [./~/moment/locale/my.js:6,0]
Condition always true [./~/moment/locale/nb.js:7,0]
Condition always true [./~/moment/locale/ne.js:6,0]
Condition always true [./~/moment/locale/nl.js:6,0]
Condition always true [./~/moment/locale/nn.js:6,0]
Condition always true [./~/moment/locale/pa-in.js:6,0]
Condition always true [./~/moment/locale/pl.js:6,0]
Condition always true [./~/moment/locale/pt-br.js:6,0]
Condition always true [./~/moment/locale/pt.js:6,0]
Condition always true [./~/moment/locale/ro.js:7,0]
Condition always true [./~/moment/locale/ru.js:8,0]
Condition always true [./~/moment/locale/se.js:6,0]
Condition always true [./~/moment/locale/si.js:6,0]
Condition always true [./~/moment/locale/sk.js:7,0]
Dropping unreachable code [./~/moment/locale/sk.js:32,0]
Dropping unreachable code [./~/moment/locale/sk.js:41,0]
Dropping unreachable code [./~/moment/locale/sk.js:50,0]
Dropping unreachable code [./~/moment/locale/sk.js:59,0]
Dropping unreachable code [./~/moment/locale/sk.js:68,0]
Condition always true [./~/moment/locale/sl.js:6,0]
Condition always true [./~/moment/locale/sq.js:8,0]
Condition always true [./~/moment/locale/sr-cyrl.js:6,0]
Condition always true [./~/moment/locale/sr.js:6,0]
Condition always true [./~/moment/locale/ss.js:6,0]
Condition always true [./~/moment/locale/sv.js:6,0]
Condition always true [./~/moment/locale/sw.js:6,0]
Condition always true [./~/moment/locale/ta.js:6,0]
Condition always true [./~/moment/locale/te.js:6,0]
Condition always true [./~/moment/locale/th.js:6,0]
Condition always true [./~/moment/locale/tl-ph.js:6,0]
Condition always true [./~/moment/locale/tlh.js:6,0]
Condition always true [./~/moment/locale/tr.js:7,0]
Condition always true [./~/moment/locale/tzl.js:6,0]
Condition always true [./~/moment/locale/tzm-latn.js:6,0]
Condition always true [./~/moment/locale/tzm.js:6,0]
Condition always true [./~/moment/locale/uk.js:7,0]
Condition always true [./~/moment/locale/uz.js:6,0]
Condition always true [./~/moment/locale/vi.js:6,0]
Condition always true [./~/moment/locale/x-pseudo.js:6,0]
Condition always true [./~/moment/locale/zh-cn.js:7,0]
Condition always true [./~/moment/locale/zh-tw.js:6,0]

---

Reusing common modules

Moment isn't the best module for highlight the most powerful feature of webpack - reusing common modules (since moment doesn't use dependencies).

Lest's consider that your application use 3 modules and each of them have some dependencies.

                   size

module1            20 kB 
  dependencies
    - moduleA      10 kB 
    - moduleB      15 kB
    - moduleC      5  kB
module1.min        50 kB

module2            10 kB 
  dependencies
    - moduleA      10 kB 
    - moduleD      5  kB
module2.min        25 kB

module3            30 kB 
  dependencies
    - moduleA      10 kB 
    - moduleC      5  kB
module3.min        45 kB

If you will only use .min version of this 3 modules you will add 50 kB + 25 kB + 45 kB = 120 kB to your application.

                   size

module1            20 kB 
  dependencies
    - moduleA      10 kB  
    - moduleB      15 kB 
    - moduleC      5  kB 
module1.min        50 kB  <-- this

module2            10 kB  
  dependencies
    - moduleA      10 kB 
    - moduleD      5  kB 
module2.min        25 kB  <-- this

module3            30 kB  
  dependencies
    - moduleA      10 kB 
    - moduleC      5  kB
module3.min        45 kB  <-- this

On the other hand if you will build with source files, common modules will be added only once. Not like previously moduleA was included 3 times and moduleC 2 times. This times to your app will be added:

                   size

module1            20 kB  <-- this
  dependencies
    - moduleA      10 kB  <-- this
    - moduleB      15 kB  <-- this
    - moduleC      5  kB  <-- this
module1.min        50 kB

module2            10 kB  <-- this
  dependencies
    - moduleA      10 kB 
    - moduleD      5  kB  <-- this
module2.min        25 kB

module3            30 kB  <-- this
  dependencies
    - moduleA      10 kB 
    - moduleC      5  kB
module3.min        45 kB

And finally with this approach you add 95 kB to your application.