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Node, accept arguments from the command line

Published Aug 14 2018

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You can pass any number of arguments when invoking a Node.js application using

node app.js

Arguments can be standalone or have a key and a value.

For example:

node app.js flavio

or

node app.js name=flavio

This changes how you will retrieve this value in the Node code.

The way you retrieve it is using the process object built into Node.

It exposes an argv property, which is an array that contains all the command line invocation arguments.

The first argument is the full path of the node command.

The second element is the full path of the file being executed.

All the additional arguments are present from the third position going forward.

You can iterate over all the arguments (including the node path and the file path) using a loop:

process.argv.forEach((val, index) => {
  console.log(`${index}: ${val}`)
})

You can get only the additional arguments by creating a new array that excludes the first 2 params:

const args = process.argv.slice(2)

If you have one argument without an index name, like this:

node app.js flavio

you can access it using

const args = process.argv.slice(2)
args[0]

In this case:

node app.js name=flavio

args[0] is name=flavio, and you need to parse it.

The best way to do so is by using the minimist library, which helps dealing with arguments:

const args = require('minimist')(process.argv.slice(2))
args['name'] //flavio

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