Edit package.json from command line

I'm trying to add or edit a variable in my package.json from a shell script. So if i have a package.json like this:

{
  "name": "my-project",
  "description": "Project by @DerZyklop",
  "version": "0.0.0",
  ...

I want a command like

npm config set foo bar

that adds a new field like

{
  "name": "my-project",
  "description": "Project by @DerZyklop",
  "foo": "bar",
  "version": "0.0.0",
  ...

...but unfortunately npm config set just edits the ~/.npmrc and not my package.json.

The package.json is just a json file, so you could use the tool json. To install it use:

npm install -g json

Then you can edit a file in-place. More information here.

Example

$ cat package.json
{
  "name": "my-project",
  "description": "Project by @DerZyklop",
  "version": "0.0.0"
}

$ json -I -f package.json -e "this.foo=\"bar\""
json: updated "package.json" in-place

$ cat package.json
{
  "name": "my-project",
  "description": "Project by @DerZyklop",
  "version": "0.0.0",
  "foo": "bar"
}

If you don't want to install sponge or json, you can also do

echo "`jq '.foo="bar"' package.json`" > package.json

If you don't want to install anything, you can also use a one-line script to modify the package.json:

node -e "let pkg=require('./package.json'); pkg.homepage='${CI_PAGES_URL}'; require('fs').writeFileSync('package.json', JSON.stringify(pkg, null, 2));"

You can also use jq and sponge (moreutils package) like this :

jq '.foo="bar"' package.json | sponge package.json

With an environment variable :

jq --arg h "$HOMEPAGE" '.homepage=$h' package.json | sponge package.json