cordova-browser/node_modules/mime/build/build.js

cordova-browser release

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));