how can i pass arguments from the command line to npm and grunt?

Let’s say our contrived project directory is structured as follows:

.
├── Gruntfile.js
├── assets
│   └── zip
│       ├── file1.zip
│       ├── file2.zip
│       └── file3.zip
├── node_modules
│   └── ...
└── package.json

Then consider the following Gruntfile.js example that utilizes grunt-contrib-copy:

Gruntfile.js

module.exports = function(grunt) {

  const target = grunt.option('target') || 'foobar'; // default dir is `foobar`.

  grunt.loadNpmTasks('grunt-contrib-copy');


  grunt.initConfig({
    copy: {
      zips: {
        files: [{
          expand: true,
          cwd: 'assets/zip',
          src: '*.zip',
          dest: 'projects/' + target
        }]
      }
    }
  });

  grunt.registerTask('copy-zips', [ 'copy:zips' ]);

};

The output via the grunt command.

1. If we cd to the project directory and run the following grunt command:

   grunt copy-zips
   

   the following folders (projects/foobar) are created in the root of the project directory.

   Results Example A

   .
   ├── ...
   └── projects
       └── foobar
           ├── file1.zip
           ├── file2.zip
           └── file3.zip
   

   Note the default foobar folder has been created containing a copy of the *.zip files. The folder was named foobar because we DID NOT provide an argument via the command line.

2. Next, If we cd to the project directory again and run the following grunt command:

   grunt copy-zips --target=my-folder-name
   

   the following folders (projects/my-folder-name) are created in the root of the project directory.

   Results Example B

   .
   ├── ...
   └── projects
       └── my-folder-name
           ├── file1.zip
           ├── file2.zip
           └── file3.zip
   

   Note This time the my-folder-name folder has been created containing a copy of the *.zip files because we provided the --target=my-folder-name argument/option.

The output via the npm command.

Firstly let’s configure the scripts section in the projects package.json as follows:

package,json

{
  ...
  "scripts": {
    "copy-zips": "grunt copy-zips"
  },
  ...
}

1. If we cd to the project directory and run the following npm command:

   npm run copy-zips
   

   we yield the same results as shown in the aforementioned Results Example A section.

2. Next, If we cd to the project directory again and run the following npm command:

   npm run copy-zips -- --target=my-folder-name
   

   we yield the same results as shown in the aforementioned Results Example B section.

   Note: The additional -- option between npm run copy-zips and the argument --target=my-folder-name.

   The npm docs describe the -- option as follows:

   As of [email protected], you can use custom arguments when executing scripts. The special option -- is used by getopt to delimit the end of the options. npm will pass all the arguments after the -- directly to your script:

---

Additional note:

If you don’t want to create the my-folder-name folder inside the projects folder, and instead you want to create the my-folder-name folder in the root of the project directory, then you can redefine the dest property in the copy task as follows:

Gruntfile.js

  // ...

  grunt.initConfig({
    copy: {
      zips: {
        files: [{
          expand: true,
          cwd: 'assets/zip',
          src: '*.zip',
          dest: target // <-----
        }]
      }
    }
  });

  // ...

Running the same command:

npm run copy-zips -- --target=my-folder-name

yields the following result:

.
├── ...
└── my-folder-name
    ├── file1.zip
    ├── file2.zip
    └── file3.zip