var traverser = require('traverser')
  , branches = []

function branch(props){
  if(!props.reference) //since we check for references with will work in cyclic graphs, without stackoverflows.
    branches.push(props.value)

  props.each()//continue working through the children of this object.
}

traverser([1,2,{},3,["x"]],{branch: branch})

console.log(branches)

var traverser = require('traverser')

exports.leaves = leaves

function leaves (obj){
    var leaves = []

    function leaf(props){
      leaves.push(props.value)
    }

    traverser(obj,{leaf: leaf})
    return leaves
}

traverser([1,2,{},3,["x"]],{leaf: leaves})

console.log(leaves([1,2,{},3,["x"]]))
//[1,2,3,'x']

options: (each of the following is optional)
{
  branch: function to call on a branch of the tree (by default, where typeof == 'object'
, leaf: function to call on primitives and functions
, isBranch: return true if current value should be treated as a branch
}

{
  value: this object
, parent: object which this item is a property of. (null if your on the root object)
, key: key of this item on parent. (null if your on the root object)
, path: [list of keys from root object to current item]
, reference: true if this object is a repeat
, circular: true if this object is in the ancestors list.
, seen: list of objects seen so far
, ancestors: list of objects between value and root object.

//when your in the branch function, you need to call one of the following to iterate over the children.
//none of these require an argument.

, each: iterate over each property
, find: iterate untill the first truthy return, returns the item.
, map: collects return values into an Array
, copy: copies objects, preserving whether it's a {} or a []
, max: iterate over all properties and return max return value
, min: iterate over all properties and return min return value
}