transform (map) function

transform.js

var transform = function(collection, predicate){
  if (Array.isArray(collection)){
    return collection.map(predicate);
  } else if (typeof collection === 'string'){
    collection = collection.split('');
    return collection.map(predicate).join('');
  } else if (typeof collection === 'object'){
    return Object.keys(collection).reduce(function(results, property){
      results[property] = predicate(collection[property]);
      return results;
    }, {});
  }
};