[ NPM 01 ] js包管理工具 基础

Node Package Manager

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npm -v : show the version , or npm --version

In the nodejs or javaScript world , package.json is the most important file, it manifest file with app info, list dependencies, specify version and so on.

1 Basic Usage

1.1 Init

• just npm init, gonna create package.json file, and need to choose package name, entry point(lots of time it's index.js), and other things.

• if it's ok to skip all questions, just npm init --yes will keep default answers.

  • the npm system default value will be storaged in file .npmrc, path: /Users/macUser/.npmrc, if put some value in it first: npm config set init-author-name "my name", then when use npm init -y, the author will read this config file automaticlly.(also can set init-license and so on).

1.2 download dependencies

• npm install lodash --save , if without --save, it will just download this package to folder node_modules, but do not add this dependency into the file package.json

• run npm install when download a new project.

• npm install gulp gulp-sass --save-dev will create dev dependencies, only used for dev.
  

• for dependencies and devdependencies, if we clone a new project, npm install will download all dependencies(regular and dev ), but    npm install --production will only download dependencies( only regular).

1.3 uninstall dependencies

• npm uninstall gulp --save-dev, remember to add --save-dev or --save behide the command, which make sure that package.json file will be updated.

1.4 download special version dependency

• npm install lodash@4.17.3 --save

• update dependency to the latest version: npm update lodash

1.5 Download global dependency(on the machine)

• npm install nodemon -g , which will not download into the project folder, will not add to the package.json file; use npm root -g can see where this nodemon dependency existed. (nodemon is a package wich will monitor every change in project and compile and run project after any changing, another one is live-server)

2. Semantic versioning

but for dependency, if : "lodash": "^4.17.4",

• caret symbol ^: means if this dependency's minor version or patch version been updated, it will pull the latest minor version or patch version mirror.

• tilde symbol ~: means if this dependency's patch version has been updated, it will pull the latest patch version mirror only!

• without any symbol, will just download the special version

• if it's "lodash": "*", will download the latest version mirror, whatever a new major version or others.

3. Other operation

• npm list list all dependencies

• npm list --depth 0 only one level

if add some scripts into the package.json,

except start and test can use npm start ornpm test, others all need use npm run xxx。