NPM run scripts

npm looks at a field called scripts in the package.json of a project in order to make things like npm test from the scripts.test field and npm start from the scripts.start field work.

{
    "name": "my-silly-app",
    "version": "1.2.3",
    "private": true,
    "dependencies": {
        "browserify": "~2.35.2",
        "uglifyjs": "~2.3.6"
    },
    "devDependencies": {
        "watchify": "~0.1.0",
        "catw": "~0.0.1",
        "tap": "~0.4.4"
    },
    "scripts": {
        "build-js": "browserify browser/main.js | uglifyjs -mc > static/bundle.js",
        "build-css": "cat static/pages/*.css tabs/*/*.css",
        "build": "npm run build-js && npm run build-css",
        "watch-js": "watchify browser/main.js -o static/bundle.js -dv",
        "watch-css": "catw static/pages/*.css tabs/*/*.css -o static/bundle.css -v",
        "watch": "npm run watch-js & npm run watch-css",
        "start": "node server.js",
        "test": "tap test/*.js"
    }
}

typing:

npm build-js

...in that project would be the same as typing:

npm run browserify browser/main.js | uglifyjs -mc > static/bundle.js

(because of the line under scripts that says: "build-js": "browserify browser/main.js | uglifyjs -mc > static/bundle.js",)

NPM run scripts

Source