Set script in package.json from command line

May 29, 2026 ยท View on GitHub

Summary

An npm command that lets you create a task in the scripts section of the package.json.

Example:

  • npm set-script start "http-server ."
{
  "name": "whatever-was-already-here",
  "scripts": {
    "start": "http-server .",
    "test": "some existing value"
  },
  ...
}

Motivation

Outside of personal daily use (which I think is worth it just for that), it would make educational uses much easier.

When giving instructions in a classroom setting (like in workshops) or just in tutorials, I'd prefer to say this:

"Run npm install --save-dev nw and then run npm set-script start "nw ." then run npm start."

The current way has more steps and is proned to error:

"Run npm install --save-dev nw then open the package.json file and add a scripts section with a start set to nw . then save that and go back to the command prompt/terminal and run npm start."

Especially since the npm install portion could take a long time, so if they modify the package.json while the install is still ongoing then when it completes and adds the dependency to the package.json it will overrite what they had (happens all the time for me).

Detailed Explanation

I want to be able to do this, walk away, and come back and it be done and running:

npm init -y && npm install --save-dev http-server && npm set-script start "http-server ." && npm start

Colons and hyphens are common in script names. they would look like this:

  • npm set-script test:e2e "nightwatch"
  • npm set-script test-unit "jest --config jest.config.js --coverage"

Rationale and Alternatives

  1. I could do npx nw . but there is an expectation that projects should just be npm install && npm start.
  2. I could manually edit the package.json and type in the script name and value in the scripts section. (current common approach)
  3. Someone could make a Node module/script to solve this that would need to be globally installed. But I'm the one writing this RFC and even I would never use that. I'm especially opposed to this as I don't believe to do something this basic should require poluting the global PATH, so I would never mention it in a workshop, classroom, or tutorial.

Implementation

  1. Add new top-level command at lib/set-script.js
  2. Require 2 arguments. First is the script name, second is command.
  3. Parse the package.json as an object
  4. If there is no "scripts" section, create it
  5. If the script name is already in use, store it for a warning message
  6. manifest.scripts[scriptName] = value
  7. Convert back to a happy string and save over the package.json
  8. If there was an existing script with a different value, output a warning message

Prior Art

The proposal of set-script is similar to the existing --save and --save-dev in the sense that it is a command followed by arguments that result in the modification of package.json.

  • npm install --save-dev http-server
{
  "name": "whatever-was-already-here",
  "devDependencies": {
    "http-server": "^1.0.0"
  },
  ...
}