npm script with arguments
13 Jan 2016npm is a powerful scripting tool to build your projects. It unifies all commands and let you do npm start, npm stop, npm run <script> etc., where the actual commands executed by them are defined under package.json.
Recently I’ve had the need to set some environment variables while doing npm start. npm commands allows you to pass arguments or set the env vars in several ways, but I wasn’t quite satisfied:
- loading an
.envfile, or prepending like<key>=<value> npm startisn’t elegant. npm config set <key> <value>: this is cumbersome af. Ain’t gonna write that!npm start --<key>=<value>: really close to what I want! But it actually sets$npm_config_<key>instead of$key.
My use case was to start my bots of different names, say:
npm startwould deploy the default bot,npm start --bot=veronicawould deploy the other bot named veronica
I fiddled with npm and bash for hours and got it figured out. Basically we use the commands above, internally these would happen:
$npm_config_botwould be set only if--bot=veronicais passed.bashchecks if$npm_config_botis set; if so it sets the$bot=veronica; else it sets the default$bot=jarvis- then the deploy script runs with the
$botvariable.
Below is my snippet from package.json:
{
"scripts": {
"start": "npm run deploy",
"deploy": "if [ $npm_config_bot ]; then bot=$npm_config_bot; echo Bot is SET to: $bot; else bot=peppurr; echo Bot is DEFAULTED to $bot; fi; DEPLOY=.keys-$bot forever start --uid $bot index.js"
}
}
Beware that if the command is split into separate npm scripts, due to the local scoping you’d actually lose the $bot variable. That’s why deploy is such a long command.