Notes about npm

How to list globally installed npm packages and versions

npm list -g --depth=0

How to initialize a node package with npm

npm init

Then we need to answer all the questions. There is another way to do it and that is to use the shorthand version of init where will default all the question.

npm init -y

That command will basically say yes to all the questions

How to run locally installed binarie tools

Fist we need to install npx globally, then we need to go inside our node project folder and run the next command:

npx eslint

Here we assuming the we have eslint package installed, when we run this command we are executing the eslint executable without passing the path of it, just easy as that.

More reference: Introducing npx: an npm package runner

Note: According to the above article this executable comes with with npm version 5.2.0 by default.

How to see all available script commands in the package.json file

npm run

The other way to see all the script commands is to install ntl globally then run ntl command inside the project, the result will be a nice menu where you can choose which script task run.

How to know where npm will install the executables

npm bin

If we want to know where npm install the executables globally we use instead:

npm bin -g

Reference: npm bin documentation

How to see the all the environment values available

npm run env

The env script is a special built-in command that can be used to list environment variables that will be available to the script at runtime. If an "env" command is defined in your package it will take precedence over the built-in.

If we are using bash, we can run the next command to filtering the result:

npm run env | grep npm

How to run scripts in series in npm

We use && to concat the scripts like this:

npm run eslint && npm run somethingelse

If eslint fail the process stop right there and it will not continue to somethingelse

How to run scripts in parallel

We use a single &:

npm run script1 & npm run script2 & wait

Note: It's important to end with & wait to allow to cancel all the process with Control + C. Also we can install packages to allow this for example npm-run-all

Using npm-run-all tool

To run scripts parallel we can use npm-run-all --parallel or run-p shorthand:

npm-run-all --parallel script1 script2

Parallel shorthand way:

run-p script1 script2

The next one is how to run the scripts in series using npm-run-all or run-s shorthand:

npm-run-all script1 script2

Serie shorthand way:

run-s script1 script2

Note: If we want more info about the usage of npm-run-all please go the npm-rull-all documentation

How to run a set of similar npm scripts with a wildcard

First lets see an abstraction of a package.json file

{
  "scripts": {
    "test": "npm-run-all eslint stylelint",
    "eslint": "eslint --cache --fix ./",
    "stylelint": "stylelint \"**/*.scss\" --syntax scss"
  }
}

We can change the above with:

{
  "scripts": {
    "test": "npm-run-all lint:*",
    "lint:js": "eslint --cache --fix ./",
    "lint:css": "stylelint \"**/*.scss\" --syntax scss",
    "lint:css:fix": "stylefmt -R src/"
  }
}

The * indicates npm will run any script that matches the pattern. In this case will run lint:js and lint:css but not the lint:css:fix. If we want to match all we use instead:

{
  "scripts": {
    "test": "npm-run-all lint:**",
    "lint:js": "eslint --cache --fix ./",
    "lint:css": "stylelint \"**/*.scss\" --syntax scss",
    "lint:css:fix": "stylefmt -R src/"
  }
}

How to run scripts before or after another

We prefix the names of the scripts with pre or post

{
  "scripts": {
    "pretest": "npm run run-this-before-test",
    "test": "npm-run-all eslint stylelint",
    "eslint": "eslint --cache --fix ./",
    "posteslint": "npm run run-this-after-eslint"
  }
}

How to pass arguments to npm scripts

{
  "scripts": {
    "script1": "npm run script2 -- --watch",
    "script2": "npm run someCommand"
  }
}

npm will pass all the arguments after the -- directly to script2

Note: more information in npm-run-script docs

How to pipe data from one npm script to another

We use the | character

{
  "scripts": {
    "script1": "npm run a | npm run b-with-passing-data-from-a | npm run so-on"
  }
}

Note: More information in How to Use npm as a Build Tool search for Streaming to multiple tasks.

How to run npm scripts when files change with onchange

Not all executables support watch option, in that cases we can use onchange

{
  "scripts": {
    "watch:lint": "onchange \"**/*.js\" -- npm run lint",
    "lint": "eslint --cache --fix ./"
  }
}

In this case we are watching all the js files and when something change in any of those files it will run the lint script

How to use package.json variables in npm scripts

We reference a variable just using the $ symbol.

{
  "main": "index.js",
  "scripts": {
    "start": "node $npm_package_main"
  }
}

In this sample when we run the start script it will run the code in index.js file. Also we can use any environment variable.

Reference: Sample from variables in npm scripts

Note: If we want to use the $ symbol in Windows that will fail we need to use a cross environment way to do it. There is a package cross-var, so the final result of the last sample will be:

{
  "main": "index.js",
  "scripts": {
    "start": "cross-var \"node $npm_package_main\""
  }
}

How to use custom config settings in your npm scripts

{
  "main": "index.js",
  "config": {
    "domain": "localhost:8000"
  },
  "scripts": {
    "start": "cross-var \"node $npm_package_main --domain $npm_package_config_domain\""
  }
}

Reference: Sample from variables in npm scripts

We can list all configuration variables with:

npm config list

You can override a config value with:

npm config set <key> <new-value>

If we want to delete an override we just run:

npm config delete <key>

How to run npm scripts with git hooks

Note: More information in Prevent Bad Commits with husky

How to change the level of console output when running npm scripts

We can accomplish this using -s silent flag to minimize the console output.

npm run script-command -s

There are other flags that we can use, please see this reference and this one to see the list.

How to make npm scripts cross-environment friendly

If want to use environment variable in a cross environment way we can use cross-env package to define environment variables in our scripts.

A sample to how to use it

{
  "scripts": {
    "build": "cross-env \"NODE_ENV=production webpack --config build/webpack.config.js\""
  }
}

and if we want to delete using a similar approach we can use rimraf instead of rm -rf.

{
  "scripts": {
    "clean": "rimraf folder-to-clean"
  }
}

If we use the open command we can use opn-cli package that provide a similar approach in a cross environment way

{
  "scripts": {
    "opensite": "opn some-folder/index.html"
  }
}

How to list the local installed packages

npm ls name-of-package

The ouput will let us know if the package exists or not. If we want to search for a package globally, the only thing that we need to do is to run the same command but with -g at the end.

How to check the version of a Node Module

npm v create-react-app version

The above command will check the current version of create-react-app, if we want to see all the versions available, we can run:

npm v create-react-app version

Or if we want to see the different versions but seeing also the tags, run:

npm v create-react-app

How to install node packages using shortcuts

To install a package to the dependencies property, we use -S

npm i eslint -S

If we want to install a node package but this time to devDependencies property use -D instead

npm i eslint -D

If we are in bash we can install multiple packages using bash brace expansion:

npm i babel{-cli,-preset-env,-plugin-trasform-object-rest-spread} -Ds

This time we are using Ds to keep the log in silence mode.

How to install a dependency without modify the package.json file

If we want to install something without modify the package.json file we use the --no-save flag:

npm i my-package --no-save

If we want to only modify the package.json but not the package.lock.json file, we use --no-shrinkwrap:

npm i my-package --no-shrinkwrap

References:

• npm doc