What is the difference between npm install and npm run build

Question

What is the difference between npm install and npm run build    I have noticed in my project that sometimes npm starts failing when npm install is performed  but  upon running npm run build  it works just fine    How does the inner workings of these two targets namely install and run build differ

User · Accepted Answer

npm install installs dependencies into the node modules  directory  for the node project you re working on  You can call install on another node js project  module   to install it as a dependency for your project  npm run build does nothing unless you specify what  quot build quot  does in your package json file  It lets you perform any necessary building prep tasks for your project  prior to it being used in another project  npm build is an internal command and is called by link and install commands  according to the documentation for build   This is the plumbing command called by npm link and npm install   You will not be calling npm build normally as it is used internally to build native C C   Node addons using node-gyp

User · Answer

The main difference is      npm install is a npm cli-command which does the predefined thing i e  as written by Churro  to install dependencies specified inside package json   npm run command-name or npm run-script command-name   ex  npm run build   is also a cli-command predefined to run your custom scripts with the name specified in place of  quot command-name quot   So  in this case npm run build is a custom script command with the name  quot build quot  and will do anything specified inside it  for instance echo  hello world  given in below example package json    Ponits to note    One more thing  npm build and npm run build are two different things  npm run build will do custom work written inside package json and npm build is a pre-defined script  not available to use directly   You cannot specify some thing inside custom build script  npm run build  script and expect npm build to do the same  Try following thing to verify in your package json     quot name quot    quot demo quot    quot version quot    quot 1 0 0 quot    quot description quot    quot  quot    quot main quot    quot index js quot    quot scripts quot      quot build quot   quot echo  hello build  quot      quot keywords quot        quot author quot    quot  quot    quot license quot    quot ISC quot    quot devDependencies quot        quot dependencies quot          and run npm run build and npm build one by one and you will see the difference  For more about commands kindly follow npm documentation  Cheers

User · Answer

NPM in 2019 npm build no longer exists  You must call npm run build now  More info below  TLDR  npm install  installs dependencies  then calls the install from the package json scripts field  npm run build  runs the build field from the package json scripts field   NPM Scripts Field https   docs npmjs com misc scripts There are many things you can put into the npm package json scripts field  Check out the documentation link above more above the lifecycle of the scripts - most have pre and post hooks that you can run scripts before after install  publish  uninstall  test  start  stop  shrinkwrap  version   To Complicate Things  npm install is not the same as npm run install npm install installs package json dependencies  then runs the package json scripts install   Essentially calls npm run install after dependencies are installed    npm run install only runs the package json scripts install  it will not install dependencies  npm build used to be a valid command  used to be the same as npm run build  but it no longer is  it is now an internal command  If you run it you ll get  npm WARN build npm build called with no arguments  Did you mean to npm run-script build  You can read more on the documentation  https   docs npmjs com cli build   Extra Notes There are still two top level commands that will run scripts  they are   npm start which is the same as npm run start npm test    gt  npm run test

User · Answer

npm install installs the depedendencies in your package json config  npm run build runs the script  build  and created a script which runs your application - let s say server js npm start runs the  start  script which will then be  node server js    It s difficult to tell exactly what the issue was but basically if you look at your scripts configuration  I would guess that  build  uses some kind of build tool to create your application while  start  assumes the build has been done but then fails if the file is not there   You are probably using bower or grunt - I seem to remember that a typical grunt application will have defined those scripts as well as a  clean  script to delete the last build   Build tools tend to create a file in a bin   dist   or build  folder which the start script then calls - e g   node build server js   When your npm start fails  it is probably because you called npm clean or similar to delete the latest build so your application file is not present causing npm start to fail   npm build s source code - to touch on the discussion in this question - is in github for you to have a look at if you like  If you run npm build directly and you have a  build  script defined  it will exit with an error asking you to call your build script as npm run-script build so it s not the same as npm run script    I m not quite sure what npm build does  but it seems to be related to postinstall and packaging scripts in dependencies  I assume that this might be making sure that any CLI build scripts s or native libraries required by dependencies are built for the specific environment after downloading the package  This will be why link and install call this script

[node.js] What is the difference between npm install and npm run build?

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