function flattenDeep(array) {
	      var length = array ? array.length : 0;
	      return length ? baseFlatten(array, true) : [];
	    }
Recursively flattens a nested array.

@static
@memberOf _
@category Array
@param {Array} array The array to recursively flatten.
@returns {Array} Returns the new flattened array.
@example

_.flattenDeep([1, [2, 3, [4]]]);
// => [1, 2, 3, 4]