example.js

//lets say you want to find the property on the `resp` object
//that contains the url of the request

request.get('http://example.com/foo/bar', (err, resp, body) => {
  console.dir(findMatchingProperty(resp, v => typeof v === 'string' && v.match(/\/foo\/bar/)));
});


/**
The result is:

[ '.request.path',
  '.request.href',
  '.request.uri.path',
  '.request.uri.href',
  '.request.uri.pathname',
  '.socket._httpMessage.path',
  '.socket._httpMessage._header' ]
 */

findMatchingProperty.js

/**
 * This functions allows you to find a property in a graph
 * of objects matching a condition.
 *
 * This is specially useful when you have a complex object
 * and you know it has a property with a value but you don't
 * know the exact name of the property.
 *
 * @param input the starting point
 * @param func the function to match the condition
 * @param analyzed ignore this parameter, it is used only to avoid walking in circles.
 */
function findMatchingProperty(input, func, analyzed) {
  analyzed = analyzed || [];
  const results = [];
  if (typeof input === 'undefined') { return results; }

  if (analyzed.indexOf(input) > -1) { return results; }
  analyzed.push(input);

  if (Array.isArray(input)) {
    input.forEach((val, index) => {
      if (func(val)) {
        results.push(`[${index}]`);
      } else {
        findMatchingProperty(val, func, analyzed).forEach(m => results.push(`[${index}]${m}`))
      }
    });
  } else if (typeof input === 'object') {
    for(var name in input) {
      var val = input[name];
      if (func(val)) {
        results.push(`.${name}`);
      } else {
        findMatchingProperty(val, func, analyzed).forEach(m => results.push(`.${name}${m}`));
      }
    }
  }

  results.sort((a, b) => a.length - b.length);

  return results;
}