Merge two objects, similar to $.extend(true). Requires underscore.js.

merge-objects.js

function mergeObjects (target, source) {
  var prop;

  for (prop in source) {
    if (source.hasOwnProperty(prop)) {
      if (_.isObject(target[prop]) && _.isObject(source[prop])) {
        mergeObjects(target[prop], source[prop]);
      } else {
        target[prop] = source[prop];
      }
    }
  }
};