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yarn install vs npm install

When we run npm install , the dependencies are installed sequentially, one after another. The output logs in the terminal are informative but a bit hard to read. To install the packages with Yarn, we run the yarn command. Yarn installs packages in parallel, which is one of the reasons it’s quicker than npm.

why yarn

Yarn — a fast, reliable, and secure alternative npm client.


For continuous integration environments, which need to be sandboxed and cut off from the internet for security and reliability reasons. While npm has to connect to npm server to download, but yarn can use local ones.

Why not npm?

The npm client installs dependencies into the node_modules directory non-deterministically. This means that based on the order dependencies are installed, the structure of a node_modules directory could be different from one person to another. These differences can cause “works on my machine” bugs that take a long time to hunt down.

How yarn work

The install process is broken down into three steps:


Yarn starts resolving dependencies by making requests to the registry and recursively looking up each dependency.


Next, Yarn looks in a global cache directory to see if the package needed has already been downloaded. If it hasn’t, Yarn fetches the tarball for the package and places it in the global cache so it can work offline and won’t need to download dependencies more than once. Dependencies can also be placed in source control as tarballs for full offline installs.


Finally, Yarn links everything together by copying all the files needed from the global cache into the local node_modules directory.

Yarn resolves these issues around versioning and non-determinism by using lockfiles and an install algorithm that is deterministic and reliable. These lockfiles lock the installed dependencies to a specific version, and ensure that every install results in the exact same file structure in node_modules across all machines. The written lockfile uses a concise format with ordered keys to ensure that changes are minimal and review is simple.

yarn why

To show a Library loaded as dependencies

yarn why redux
yarn why v1.22.18
[1/4] 🤔  Why do we have the module "redux"...?
[2/4] 🚚  Initialising dependency graph...
[3/4] 🔍  Finding dependency...
[4/4] 🚡  Calculating file sizes...
=> Found "redux@4.1.2"
info Has been hoisted to "redux"
info Reasons this module exists
   - Specified in "dependencies"
   - Hoisted from "react-beautiful-dnd#redux"
   - Hoisted from "react-beautiful-dnd#react-redux#@types#react-redux#redux"
info Disk size without dependencies: "240KB"
info Disk size with unique dependencies: "1.06MB"
info Disk size with transitive dependencies: "1.1MB"
info Number of shared dependencies: 2
✨  Done in 0.34s.

skip optional

In some extents, maybe for performance perspective or errors in some non-mandatory library, you can skip those optional libraries during install. For example, fsevents is dealt differently in mac and other linux system. Linux system ignores fsevents whereas mac install it. As the above error message states that fsevents is optional and it is skipped in installation process.

You can run npm install --no-optional

Why node-gyp used in nodejs

Basically, node-gyp is like make. It’s a tool used to control the compilation process of C++ projects. Only, it’s designed specifically for node.js addons (modules written in C++). So moving to a different system may work if it uses the same CPU. Moving to a different OS or CPU (for example from x86 to ARM) won’t work. For Linux, moving to a different distro of different version of the same distro may or may not work. I’m not 100% sure if moving to a different version of node.js would work

node-gyp is a tool which compiles Node.js Addons. Node.js Addons are native Node.js Modules, written in C or C++, which therefore need to be compiled on your machine. After they are compiled with tools like node-gyp, their functionality can be accessed via require(), just as any other Node.js Module.