Get a nested object property by passing a dot notation string as the property name

getProperty.js

/**
 * A function to take a string written in dot notation style, and use it to
 * find a nested object property inside of an object.
 *
 * Useful in a plugin or module that accepts a JSON array of objects, but
 * you want to let the user specify where to find various bits of data
 * inside of each custom object instead of forcing a standardized
 * property list.
 *
 * @param String nested A dot notation style parameter reference (ie "urls.small")
 * @param Object object (optional) The object to search
 *
 * @return the value of the property in question
 */

function getProperty( propertyName, object ) {
  var parts = propertyName.split( "." ),
    length = parts.length,
    i,
    property = object || this;

  for ( i = 0; i < length; i++ ) {
    property = property[parts[i]];
  }

  return property;
}

other trick
https://stackoverflow.com/questions/6906108/in-javascript-how-can-i-dynamically-get-a-nested-property-of-an-object
and https://stackoverflow.com/questions/8051975/access-object-child-properties-using-a-dot-notation-string