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Fix slow ZSH startup due to NVM

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NVM can really be helpful when dealing with older projects. But there’s a problem, still. The nvm installation adds a portion of code to your .zshrc to enable autocompletion. This, in turn, slows the startup of your shell quite a lot.
But we can easily fix this slow zsh startup! Instead of always loading your nvm autocompletion, we can command oh-my-zsh to just load nvm ressources on-demand, also known as lazy-loading.

TLDR:

Open your .zshrc, add the line export NVM_LAZY=1 and, somewhere below, add nvm to your list of oh-my-zsh plugins.

How do I check if just NVM slows my ZSH startup?

That’s easy. In your ~/.zshrc you can simply add zmodload zsh/zprof as first line and zprof as last line.
This will prove you a nice output on which plugin caused what delay.

So go ahead, add these both lines to your shell startup script and time your shell startup with time zsh -i -c exit. This will start your ZSH and execute the exit command. Scroll a bit up and your zsh output should blame nvm:

Slow startup on ZSH after installing NVM
NVM is responsible for 89.5% of my shell startup time.

Bad, right? That’s almost 90% startup time caused by a single tool I don’t use that much. So let’s fix this!

How do I fix the slow zsh startup?

As the normal ZSH user, you probably already have different plugins provided by oh-my-zsh. If not, really, go ahead and get yourself some nice plugins! It’s a community driven aggregator of many many great plugins.

The plugin we need now is the nvm plugin. It’s already included in oh-my-zsh and should be activated in your plugins array somewhere in your .zshrc. But you also want to add the line export NVM_LAZY=1, which enables the lazy-loading mode. This mode only sources and activates nvm when its necessary, for example in directories that contain a .nvmrc file. So, in conclusion, add/modify the following in your zsh startup script:

export NVM_LAZY=1 plugins=( nvm // [...] ) // [...]
Code language: JavaScript (javascript)

Also, be sure to remove the lines added by nvm, they should be somewhere at the bottom of your script, mine looked like:

export NVM_DIR="$HOME/.nvm" [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh" # This loads nvm [ -s "$NVM_DIR/bash_completion" ] && \. "$NVM_DIR/bash_completion" # This loads nvm bash_completion
Code language: PHP (php)

Checking fixed startup times

Now, go to any directory that shouln’t autostart nvm and check your timings again. Mine looked like this:

Improved startup times after nvm lazy-loading
Much better, startup time is almost back to pre-nvm

As you can see above, nvm support takes now much less time to start, while still being available “on-call”.

Done!

Now you can safely remove the debugging lines we introduced to our .zshrc earlier.
Hopefully I could help you a bit with this short post, see you around for the next one 🙂

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