This plugin enables you to define custom values in the metadata. Why you would use it for is up to you, but here are some ideas:

• expose a node module (e.g.: Lodash) in the metadata to use it in a template
• expose process.env to your templates (NODE_ENV, etc)
• expose JSON files (e.g.: expose the package.json file similarly to how it could be done in a Gruntfile)
• expose your own JavaScript modules (e.g.: define custom helper functions)

Note that Metalsmith now has a metalsmith.metadata() method, which overlaps some areas covered by this plugin. Though metalsmith-define still proves valuable in some situations:

1. You want to define metadata but you only use the CLI version of Metalsmith (with no access to the API)
2. You use the API, but the source of your metadata is not an Object. This plugin, on the other hand, supports any iterable: Array, Class, Map, etc.

npm install metalsmith-define

metalsmith.json

{
  "plugins": {
    "metalsmith-define": {
      "production": true
    }
  }
}

const metalsmith = require('metalsmith')
const metalsmithDefine = require('metalsmith-define')

metalsmith(__dirname).use(
  metalsmithDefine({
    _: require('underscore'),
    development: true,
    pkg: require('./package.json'),
    helpers: require('./helpers.js'),
  })
)

Type: Enumerable (Array, Class, Map, Object, string, etc) Default: {}

This parameter will be iterated on all its key/value pairs either via:

• {type}.prototype.entries if the method exists (e.g., Map),
• or Object.entries for all the other types: Array, Object, etc

The pairs will be merged into the metadata object in the order in which they are being iterated on.