tastypie/node_modules/mime/build/build.js

Tastypie is a webservice API framework for Node.js based on Django's Tastypie Framework. It provides a convenient, yet powerful and highly customizable, abstraction for creating REST-style interfaces

var db = require('mime-db');

var mapByType = {};
Object.keys(db).forEach(function(key) {
  var extensions = db[key].extensions;
  if (extensions) {
    mapByType[key] = extensions;
  }
});

console.log(JSON.stringify(mapByType));