什么是 npm · 八股题库 / Drills

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一句话：Node 的包管理器 + 全球最大的包仓库。它负责装依赖、锁版本、跑脚本。

三件核心事：

装依赖—— 读 package.json 的dependencies，递归下载到 node_modules。
锁版本——package-lock.json记下每一个包的确切版本和哈希，保证队友和 CI 装出来的一模一样。它必须提交到版本库。
跑脚本——npm run dev，而且会把node_modules/.bin加到 PATH，所以能直接写vitest 而不用写全路径。

必答的两个区分：

dependencies vs devDependencies—— 前者是运行时需要的（React），后者只在开发和构建时需要（TypeScript、测试框架、打包工具）。生产安装可以用npm ci --omit=dev 跳过后者。
npm install vs npm ci——install 会在需要时更新 lock 文件；ci 严格按 lock 装，对不上就直接报错。CI 里应该用 ci。

会追问：「^1.2.3 和~1.2.3 什么区别？」——^ 允许小版本和补丁升级（<2.0.0），~ 只允许补丁（<1.3.0）。正是因为 ^ 的存在， lock 文件才必不可少—— 否则不同时间装出来的版本会不同。

In one line: Node’s package manager, plus the largest package registry in the world. It installs dependencies, pins versions and runs scripts.

Three core jobs:

Install dependencies — read dependencies out of package.json and download the whole tree into node_modules.
Pin versions — package-lock.json records the exact version and hash of every package, so a teammate and CI install precisely what you did. It has to be committed.
Run scripts — npm run dev. It also puts node_modules/.bin on the PATH, which is why you can write vitest instead of a full path.

Two distinctions you must be able to make:

dependencies vs devDependencies — the first is what you need at runtime (React), the second only while developing and building (TypeScript, the test runner, the bundler). A production install can skip the second with npm ci --omit=dev.
npm install vs npm ci — install will update the lock file when it has to; ci installs strictly from the lock and errors out if the two disagree. CI should use ci.

Follow-up: “What is the difference between ^1.2.3 and ~1.2.3?” — ^ allows minor and patch upgrades (<2.0.0), ~ allows patches only (<1.3.0). It is precisely because ^ exists that the lock file is indispensable — otherwise installing on two different days gives you two different trees.