Npm 安装 vs 更新-有什么区别？

Question

What is the practical difference between npm install and npm update? When should I use which?

转载于:https://stackoverflow.com/questions/12478679/npm-install-vs-update-whats-the-difference

Answer 1

The difference between npm install and npm update handling of package versions specified in package.json:

{
  "name":          "my-project",
  "version":       "1.0",                             // install   update
  "dependencies":  {                                  // ------------------
    "already-installed-versionless-module":  "*",     // ignores   "1.0" -> "1.1"
    "already-installed-semver-module":       "^1.4.3" // ignores   "1.4.3" -> "1.5.2"
    "already-installed-versioned-module":    "3.4.1"  // ignores   ignores
    "not-yet-installed-versionless-module":  "*",     // installs  installs
    "not-yet-installed-semver-module":       "^4.2.1" // installs  installs
    "not-yet-installed-versioned-module":    "2.7.8"  // installs  installs
  }
}

Summary: The only big difference is that an already installed module with fuzzy versioning ...

• gets ignored by npm install
• gets updated by npm update

Additionally: install and update by default handle devDependencies differently

• npm install will install/update devDependencies unless --production flag is added
• npm update will ignore devDependencies unless --dev flag is added

---

Why use npm install at all?

Because npm install does more when you look besides handling your dependencies in package.json. As you can see in npm install you can ...

• manually install node-modules
• set them as global (which puts them in the shell's PATH) using npm install -g <name>
• install certain versions described by git tags
• install from a git url
• force a reinstall with --force