動機

Saving disk space

使用 npm 時，若您有 100 件專案都使用了同個依附套件，磁碟中就會有 100 份該套件的副本。 反之，有了 pnpm，該依附套件會被儲存在一個由內容定址的儲存區，因此：

1. 如果您同時需要該依附套件的不同版本，只有存在差異的檔案才會被加入儲存區。 For instance, if it has 100 files, and a new version has a change in only one of those files, pnpm update will only add 1 new file to the store, instead of cloning the entire dependency just for the singular change.
2. 所有依賴套件的檔案將被儲存在磁碟中的單一位置。 當依賴套件被 安裝時，依賴套件的檔案會被硬鏈結至該位置，不會消耗 額外的磁碟空間。 這將允許您在不同專案之間共享相同版本的依賴套件。

由於上述原因，您將節省大量的磁碟空間，這將與您的 專案和依賴套件的數量成正比，並且將大幅提升安裝的速度！

Boosting installation speed

pnpm perfoms installation in three stages:

1. Dependency resolution. All required dependencies are identified and fetched to the store.
2. Directory structure calculation. The node_modules directory structure is calculated based on the dependencies.
3. Linking dependencies. All remaining dependencies are fetched and hard linked from the store to node_modules.

This approach is significantly faster than the traditional three-stage installation process of resolving, fetching, and writing all dependencies to node_modules.

Creating a non-flat node_modules directory

When installing dependencies with npm or Yarn Classic, all packages are hoisted to the root of the modules directory. As a result, source code has access to dependencies that are not added as dependencies to the project.

By default, pnpm uses symlinks to add only the direct dependencies of the project into the root of the modules directory.

If you'd like more details about the unique node_modules structure that pnpm creates and why it works fine with the Node.js ecosystem, read:

• Flat node_modules is not the only way
• Symlinked node_modules structure

提示

If your tooling doesn't work well with symlinks, you may still use pnpm and set the node-linker setting to hoisted. This will instruct pnpm to create a node_modules directory that is similar to those created by npm and Yarn Classic.