Is it possible to install npm package only if it has not been already installed?

Question

Is it possible to install npm package only if it has not been already installed?

I need this to speed up test on CircleCI, but when I run npm install protractor@2.1.0 etc. it always downloads things and installs them from scracth, however, node_modules folder with all modules is already present at the moment of running commands (cached from previous build) and protractor --version etc. shows the needed version of the package.

Its perfect to have some one-line command like this:

protractor --version || npm install -g protractor@2.1.0

but the one that will also check version of the package.

I need check version of currently installed package, preferably not writing full path to the package. multiple different environments, different paths etc. — kovpack, Jun 05 '15 at 13:25
@bishop's answer works well when you want to check if something is installed globally — dimiguel, Feb 22 '17 at 07:45

score 56 · Answer 1 · answered Aug 23 '17 at 07:15

56

You could try npm list protractor || npm install protractor@2.1.0

Where npm list protractor is used to find protractor package.

If the package is not found, it will return npm ERR! code 1 and do npm install protractor@2.1.0 for installation

answered Aug 23 '17 at 07:15

An Nguyen

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Short and simple. Best one-liner here – Sanctus Oct 10 '19 at 18:04
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I'm on npm v6.0.1 and it doesn't appear `npm list ` quits with an error, it just returns a list with "(empty)" in it. – MattTreichel Jan 12 '21 at 21:11
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With the newer npm version, `npm list ` won't show `npm ERR! code 1` but it does exit with an error. Therefore, the whole command `npm list || npm install ` still works. – An Nguyen Jul 14 '21 at 15:49

score 23 · Accepted Answer · answered Jun 05 '15 at 13:44

23

with bash you can do

[ $(node -p "require('protractor/package.json').version") != "2.1.0" ] && npm install protractor@2.1.0

answered Jun 05 '15 at 13:44

Jerome WAGNER

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Almost perfect, as it has just turned out. It throws exception if package is not present. – kovpack Jun 05 '15 at 21:42

bishop · Answer 3 · 2017-09-13T13:51:42.903

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Function version of the excellent answer by @JeromeWAGNER:

function install_package_if_needed() {
    local p=${1:-Package required}
    local v=${2:-Version required}
    shift 2
    local i=$(node -p "require('$p/package.json').version" 2>/dev/null)
    [ "$i" == "$v" ] || npm "$@" install "$p@$v"
}

Use like:

$ install_package_if_needed protractor 2.1.0

To pass additional options to npm, specify them after the version, like so:

$ install_package_if_needed protractor 2.1.0 -g

edited Sep 13 '17 at 13:51

answered Jun 05 '15 at 14:09

bishop

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Yeap, thanx. I did something like this, but called multiple system commands from ruby. But exactly this version is not applicable for my task. – kovpack Jun 05 '15 at 21:45
Thanks for this. But needed to remove >/dev/null else $i will always be empty. – Daryl Teo Dec 13 '15 at 04:35
@DarylTeo Thanks! You're right. Not sure what I was thinking. Fixed! – bishop Dec 14 '15 at 14:35
How can this be generalized to install a package globally, if missing? At the moment it clearly does not accept `-g` flag. Thanks. – nirvana-msu Sep 13 '17 at 10:37

score 2 · Answer 4 · edited Jan 05 '17 at 12:20

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[ $(node -p "try{require('protractor/package.json').version}catch(e){}") != "2.1.0" ]  && npm install grunt

edited Jan 05 '17 at 12:20

John Weisz

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answered May 27 '16 at 00:48

theJC

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score 0 · Answer 5 · edited May 23 '17 at 12:10

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I had this same issue together with wanting to install global dependencies from any "package.json" file requiring them.

This is for a Windows development environment.

Here is my solution.

edited May 23 '17 at 12:10

Community

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answered Dec 31 '15 at 19:06

sthames42

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Is it possible to install npm package only if it has not been already installed?

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