This is a first example.

datapackage.json

{
  "manifest_version": 1,
  "created": "2012-12-28T20:32:39.564Z",
  "scripts": [
    {
      "created": "2012-12-30T19:41:43.446Z",
      "last_modified": "2012-12-30T19:41:43.446Z",
      "language": "javascript",
      "content": "print(\"hello world\");\nprint('Fields: ', dataset.fields);\n// let's compute inflation\ndataset.data = _.map(dataset.data.slice(1), function(record, idx) {\n  record.inflation = 100 * (dataset.data[idx+1].CDKO - dataset.data[idx].CDKO)/dataset.data[idx].CDKO;\n  return record;\n});\ndataset.fields.push({id: 'inflation'});\nprint(dataset.data[0]);\nsaveDataset(dataset);\nprint('here again 6');",
      "id": "main.js"
    }
  ],
  "project_version": 1,
  "source": {
    "backend": "csv",
    "url": "http://localhost/datasets/consumer-price-index-uk/data/cpi-uk-annual.csv"
  },
  "id": "dataexplorer-528307",
  "last_modified": "2013-01-05T16:22:09.737Z",
  "gist_id": "4461651",
  "datasets": []
}