// alternative approach for testing if value is an Object

(function() {

	'use strict';

	var hash = {
		level1a: 'l1a',
		level1b: 'l1b',
		level1c: {
			level2a: 'l2a',
			level2b: {
				level3a: 'l3a'
			},
			level2c: 'l2c'
		},
		level1d: 'l1d'
	};

	var x = 1,
	flat = {};

	function flatten(nested) {

		for (var key in nested) {

			if ( isObj(nested[key]) ) {
				console.log('nested ', nested[key]);
				flatten(nested[key]);
			} else {
				flat['prop' + x] = nested[key];
				x++;
			}

		}

		return flat;

	}

	function isObj(obj) {
		return obj === Object(obj);
	}

	console.log(flatten(hash));

}());