(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.graphlib = f()}})(function(){var define,module,exports;return (function(){function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s}return e})()({1:[function(require,module,exports){
module.exports = {
  Graph: require('./lib/graph'),
  json: require('./lib/json'),
  alg: require('./lib/alg')
}

},{"./lib/alg":8,"./lib/graph":16,"./lib/json":17}],2:[function(require,module,exports){
var _ = require('../lodash')

module.exports = components

function components (g) {
  const visited = {}
  const cmpts = []
  let cmpt

  function dfs (v) {
    if (_.has(visited, v)) return
    visited[v] = true
    cmpt.push(v)
    _.each(g.successors(v), dfs)
    _.each(g.predecessors(v), dfs)
  }

  _.each(g.nodes(), function (v) {
    cmpt = []
    dfs(v)
    if (cmpt.length) {
      cmpts.push(cmpt)
    }
  })

  return cmpts
}

},{"../lodash":18}],3:[function(require,module,exports){
var _ = require('../lodash')

module.exports = dfs

/*
 * A helper that preforms a pre- or post-order traversal on the input graph
 * and returns the nodes in the order they were visited. If the graph is
 * undirected then this algorithm will navigate using neighbors. If the graph
 * is directed then this algorithm will navigate using successors.
 *
 * Order must be one of "pre" or "post".
 */
function dfs (g, vs, order) {
  if (!_.isArray(vs)) {
    vs = [vs]
  }

  var navigation = (g.isDirected() ? g.successors : g.neighbors).bind(g)

  const acc = []
  const visited = {}
  _.each(vs, function (v) {
    if (!g.hasNode(v)) {
      throw new Error('Graph does not have node: ' + v)
    }

    doDfs(g, v, order === 'post', visited, navigation, acc)
  })
  return acc
}

function doDfs (g, v, postorder, visited, navigation, acc) {
  if (!_.has(visited, v)) {
    visited[v] = true

    if (!postorder) { acc.push(v) }
    _.each(navigation(v), function (w) {
      doDfs(g, w, postorder, visited, navigation, acc)
    })
    if (postorder) { acc.push(v) }
  }
}

},{"../lodash":18}],4:[function(require,module,exports){
const dijkstra = require('./dijkstra')
const _ = require('../lodash')

module.exports = dijkstraAll

function dijkstraAll (g, weightFunc, edgeFunc) {
  return _.transform(g.nodes(), function (acc, v) {
    acc[v] = dijkstra(g, v, weightFunc, edgeFunc)
  }, {})
}

},{"../lodash":18,"./dijkstra":5}],5:[function(require,module,exports){
const _ = require('../lodash')
const PriorityQueue = require('../data/priority-queue')

module.exports = dijkstra

var DEFAULT_WEIGHT_FUNC = _.constant(1)

function dijkstra (g, source, weightFn, edgeFn) {
  return runDijkstra(g, String(source),
    weightFn || DEFAULT_WEIGHT_FUNC,
    edgeFn || function (v) { return g.outEdges(v) })
}

function runDijkstra (g, source, weightFn, edgeFn) {
  const results = {}
  const pq = new PriorityQueue()
  let v, vEntry

  var updateNeighbors = function (edge) {
    const w = edge.v !== v ? edge.v : edge.w
    const wEntry = results[w]
    const weight = weightFn(edge)
    const distance = vEntry.distance + weight

    if (weight < 0) {
      throw new Error('dijkstra does not allow negative edge weights. ' +
                      'Bad edge: ' + edge + ' Weight: ' + weight)
    }

    if (distance < wEntry.distance) {
      wEntry.distance = distance
      wEntry.predecessor = v
      pq.decrease(w, distance)
    }
  }

  g.nodes().forEach(function (v) {
    var distance = v === source ? 0 : Number.POSITIVE_INFINITY
    results[v] = { distance: distance }
    pq.add(v, distance)
  })

  while (pq.size() > 0) {
    v = pq.removeMin()
    vEntry = results[v]
    if (vEntry.distance === Number.POSITIVE_INFINITY) {
      break
    }

    edgeFn(v).forEach(updateNeighbors)
  }

  return results
}

},{"../data/priority-queue":15,"../lodash":18}],6:[function(require,module,exports){
const _ = require('../lodash')
const tarjan = require('./tarjan')

module.exports = findCycles

function findCycles (g) {
  return _.filter(tarjan(g), function (cmpt) {
    return cmpt.length > 1 || (cmpt.length === 1 && g.hasEdge(cmpt[0], cmpt[0]))
  })
}

},{"../lodash":18,"./tarjan":13}],7:[function(require,module,exports){
var _ = require('../lodash')

module.exports = floydWarshall

var DEFAULT_WEIGHT_FUNC = _.constant(1)

function floydWarshall (g, weightFn, edgeFn) {
  return runFloydWarshall(g,
    weightFn || DEFAULT_WEIGHT_FUNC,
    edgeFn || function (v) { return g.outEdges(v) })
}

function runFloydWarshall (g, weightFn, edgeFn) {
  const results = {}
  const nodes = g.nodes()

  nodes.forEach(function (v) {
    results[v] = {}
    results[v][v] = { distance: 0 }
    nodes.forEach(function (w) {
      if (v !== w) {
        results[v][w] = { distance: Number.POSITIVE_INFINITY }
      }
    })
    edgeFn(v).forEach(function (edge) {
      const w = edge.v === v ? edge.w : edge.v
      const d = weightFn(edge)
      results[v][w] = { distance: d, predecessor: v }
    })
  })

  nodes.forEach(function (k) {
    var rowK = results[k]
    nodes.forEach(function (i) {
      var rowI = results[i]
      nodes.forEach(function (j) {
        var ik = rowI[k]
        var kj = rowK[j]
        var ij = rowI[j]
        var altDistance = ik.distance + kj.distance
        if (altDistance < ij.distance) {
          ij.distance = altDistance
          ij.predecessor = kj.predecessor
        }
      })
    })
  })

  return results
}

},{"../lodash":18}],8:[function(require,module,exports){
module.exports = {
  components: require('./components'),
  dijkstra: require('./dijkstra'),
  dijkstraAll: require('./dijkstra-all'),
  findCycles: require('./find-cycles'),
  floydWarshall: require('./floyd-warshall'),
  isAcyclic: require('./is-acyclic'),
  postorder: require('./postorder'),
  preorder: require('./preorder'),
  prim: require('./prim'),
  tarjan: require('./tarjan'),
  topsort: require('./topsort')
}

},{"./components":2,"./dijkstra":5,"./dijkstra-all":4,"./find-cycles":6,"./floyd-warshall":7,"./is-acyclic":9,"./postorder":10,"./preorder":11,"./prim":12,"./tarjan":13,"./topsort":14}],9:[function(require,module,exports){
var topsort = require('./topsort')

module.exports = isAcyclic

function isAcyclic (g) {
  try {
    topsort(g)
  } catch (e) {
    if (e instanceof topsort.CycleException) {
      return false
    }
    throw e
  }
  return true
}

},{"./topsort":14}],10:[function(require,module,exports){
var dfs = require('./dfs')

module.exports = postorder

function postorder (g, vs) {
  return dfs(g, vs, 'post')
}

},{"./dfs":3}],11:[function(require,module,exports){
var dfs = require('./dfs')

module.exports = preorder

function preorder (g, vs) {
  return dfs(g, vs, 'pre')
}

},{"./dfs":3}],12:[function(require,module,exports){
const _ = require('../lodash')
const Graph = require('../graph')
const PriorityQueue = require('../data/priority-queue')

module.exports = prim

function prim (g, weightFunc) {
  const result = new Graph()
  const parents = {}
  const pq = new PriorityQueue()
  let v

  function updateNeighbors (edge) {
    const w = edge.v === v ? edge.w : edge.v
    const pri = pq.priority(w)
    if (pri !== undefined) {
      var edgeWeight = weightFunc(edge)
      if (edgeWeight < pri) {
        parents[w] = v
        pq.decrease(w, edgeWeight)
      }
    }
  }

  if (g.nodeCount() === 0) {
    return result
  }

  _.each(g.nodes(), function (v) {
    pq.add(v, Number.POSITIVE_INFINITY)
    result.setNode(v)
  })

  // Start from an arbitrary node
  pq.decrease(g.nodes()[0], 0)

  var init = false
  while (pq.size() > 0) {
    v = pq.removeMin()
    if (_.has(parents, v)) {
      result.setEdge(v, parents[v])
    } else if (init) {
      throw new Error('Input graph is not connected: ' + g)
    } else {
      init = true
    }

    g.nodeEdges(v).forEach(updateNeighbors)
  }

  return result
}

},{"../data/priority-queue":15,"../graph":16,"../lodash":18}],13:[function(require,module,exports){
var _ = require('../lodash')

module.exports = tarjan

function tarjan (g) {
  let index = 0
  const stack = []
  const visited = {} // node id -> { onStack, lowlink, index }
  const results = []

  function dfs (v) {
    var entry = visited[v] = {
      onStack: true,
      lowlink: index,
      index: index++
    }
    stack.push(v)

    g.successors(v).forEach(function (w) {
      if (!_.has(visited, w)) {
        dfs(w)
        entry.lowlink = Math.min(entry.lowlink, visited[w].lowlink)
      } else if (visited[w].onStack) {
        entry.lowlink = Math.min(entry.lowlink, visited[w].index)
      }
    })

    if (entry.lowlink === entry.index) {
      const cmpt = []
      let w
      do {
        w = stack.pop()
        visited[w].onStack = false
        cmpt.push(w)
      } while (v !== w)
      results.push(cmpt)
    }
  }

  g.nodes().forEach(function (v) {
    if (!_.has(visited, v)) {
      dfs(v)
    }
  })

  return results
}

},{"../lodash":18}],14:[function(require,module,exports){
const _ = require('../lodash')

module.exports = topsort
topsort.CycleException = CycleException

function topsort (g) {
  const visited = {}
  const stack = {}
  const results = []

  function visit (node) {
    if (_.has(stack, node)) {
      throw new CycleException()
    }

    if (!_.has(visited, node)) {
      stack[node] = true
      visited[node] = true
      _.each(g.predecessors(node), visit)
      delete stack[node]
      results.push(node)
    }
  }

  _.each(g.sinks(), visit)

  if (_.size(visited) !== g.nodeCount()) {
    throw new CycleException()
  }

  return results
}

function CycleException () {}
CycleException.prototype = new Error() // must be an instance of Error to pass testing

},{"../lodash":18}],15:[function(require,module,exports){
const _ = require('../lodash')

module.exports = PriorityQueue

/**
 * A min-priority queue data structure. This algorithm is derived from Cormen,
 * et al., "Introduction to Algorithms". The basic idea of a min-priority
 * queue is that you can efficiently (in O(1) time) get the smallest key in
 * the queue. Adding and removing elements takes O(log n) time. A key can
 * have its priority decreased in O(log n) time.
 */
function PriorityQueue () {
  this._arr = []
  this._keyIndices = {}
}

/**
 * Returns the number of elements in the queue. Takes `O(1)` time.
 */
PriorityQueue.prototype.size = function () {
  return this._arr.length
}

/**
 * Returns the keys that are in the queue. Takes `O(n)` time.
 */
PriorityQueue.prototype.keys = function () {
  return this._arr.map(function (x) { return x.key })
}

/**
 * Returns `true` if **key** is in the queue and `false` if not.
 */
PriorityQueue.prototype.has = function (key) {
  return _.has(this._keyIndices, key)
}

/**
 * Returns the priority for **key**. If **key** is not present in the queue
 * then this function returns `undefined`. Takes `O(1)` time.
 *
 * @param {Object} key
 */
PriorityQueue.prototype.priority = function (key) {
  var index = this._keyIndices[key]
  if (index !== undefined) {
    return this._arr[index].priority
  }
}

/**
 * Returns the key for the minimum element in this queue. If the queue is
 * empty this function throws an Error. Takes `O(1)` time.
 */
PriorityQueue.prototype.min = function () {
  if (this.size() === 0) {
    throw new Error('Queue underflow')
  }
  return this._arr[0].key
}

/**
 * Inserts a new key into the priority queue. If the key already exists in
 * the queue this function returns `false`; otherwise it will return `true`.
 * Takes `O(n)` time.
 *
 * @param {Object} key the key to add
 * @param {Number} priority the initial priority for the key
 */
PriorityQueue.prototype.add = function (key, priority) {
  var keyIndices = this._keyIndices
  key = String(key)
  if (!_.has(keyIndices, key)) {
    var arr = this._arr
    var index = arr.length
    keyIndices[key] = index
    arr.push({key: key, priority: priority})
    this._decrease(index)
    return true
  }
  return false
}

/**
 * Removes and returns the smallest key in the queue. Takes `O(log n)` time.
 */
PriorityQueue.prototype.removeMin = function () {
  this._swap(0, this._arr.length - 1)
  var min = this._arr.pop()
  delete this._keyIndices[min.key]
  this._heapify(0)
  return min.key
}

/**
 * Decreases the priority for **key** to **priority**. If the new priority is
 * greater than the previous priority, this function will throw an Error.
 *
 * @param {Object} key the key for which to raise priority
 * @param {Number} priority the new priority for the key
 */
PriorityQueue.prototype.decrease = function (key, priority) {
  var index = this._keyIndices[key]
  if (priority > this._arr[index].priority) {
    throw new Error('New priority is greater than current priority. ' +
        'Key: ' + key + ' Old: ' + this._arr[index].priority + ' New: ' + priority)
  }
  this._arr[index].priority = priority
  this._decrease(index)
}

PriorityQueue.prototype._heapify = function (i) {
  const arr = this._arr
  const l = 2 * i
  const r = l + 1
  let largest = i
  if (l < arr.length) {
    largest = arr[l].priority < arr[largest].priority ? l : largest
    if (r < arr.length) {
      largest = arr[r].priority < arr[largest].priority ? r : largest
    }
    if (largest !== i) {
      this._swap(i, largest)
      this._heapify(largest)
    }
  }
}

PriorityQueue.prototype._decrease = function (index) {
  var arr = this._arr
  var priority = arr[index].priority
  var parent
  while (index !== 0) {
    parent = index >> 1
    if (arr[parent].priority < priority) {
      break
    }
    this._swap(index, parent)
    index = parent
  }
}

PriorityQueue.prototype._swap = function (i, j) {
  var arr = this._arr
  var keyIndices = this._keyIndices
  var origArrI = arr[i]
  var origArrJ = arr[j]
  arr[i] = origArrJ
  arr[j] = origArrI
  keyIndices[origArrJ.key] = i
  keyIndices[origArrI.key] = j
}

},{"../lodash":18}],16:[function(require,module,exports){
const _ = require('./lodash')

module.exports = Graph

const DEFAULT_EDGE_NAME = '\x00'
const GRAPH_NODE = '\x00'
const EDGE_KEY_DELIM = '\x01'

// Implementation notes:
//
//  * Node id query functions should return string ids for the nodes
//  * Edge id query functions should return an "edgeObj", edge object, that is
//    composed of enough information to uniquely identify an edge: {v, w, name}.
//  * Internally we use an "edgeId", a stringified form of the edgeObj, to
//    reference edges. This is because we need a performant way to look these
//    edges up and, object properties, which have string keys, are the closest
//    we're going to get to a performant hashtable in JavaScript.

function Graph (opts) {
  this._isDirected = _.has(opts, 'directed') ? opts.directed : true
  this._isMultigraph = _.has(opts, 'multigraph') ? opts.multigraph : false
  this._isCompound = _.has(opts, 'compound') ? opts.compound : false

  // Label for the graph itself
  this._label = undefined

  // Defaults to be set when creating a new node
  this._defaultNodeLabelFn = _.constant(undefined)

  // Defaults to be set when creating a new edge
  this._defaultEdgeLabelFn = _.constant(undefined)

  // v -> label
  this._nodes = {}

  if (this._isCompound) {
    // v -> parent
    this._parent = {}

    // v -> children
    this._children = {}
    this._children[GRAPH_NODE] = {}
  }

  // v -> edgeObj
  this._in = {}

  // u -> v -> Number
  this._preds = {}

  // v -> edgeObj
  this._out = {}

  // v -> w -> Number
  this._sucs = {}

  // e -> edgeObj
  this._edgeObjs = {}

  // e -> label
  this._edgeLabels = {}
}

/* Number of nodes in the graph. Should only be changed by the implementation. */
Graph.prototype._nodeCount = 0

/* Number of edges in the graph. Should only be changed by the implementation. */
Graph.prototype._edgeCount = 0

/* === Graph functions ========= */

Graph.prototype.isDirected = function () {
  return this._isDirected
}

Graph.prototype.isMultigraph = function () {
  return this._isMultigraph
}

Graph.prototype.isCompound = function () {
  return this._isCompound
}

Graph.prototype.setGraph = function (label) {
  this._label = label
  return this
}

Graph.prototype.graph = function () {
  return this._label
}

/* === Node functions ========== */

Graph.prototype.setDefaultNodeLabel = function (newDefault) {
  if (!_.isFunction(newDefault)) {
    newDefault = _.constant(newDefault)
  }
  this._defaultNodeLabelFn = newDefault
  return this
}

Graph.prototype.nodeCount = function () {
  return this._nodeCount
}

Graph.prototype.nodes = function () {
  return _.keys(this._nodes)
}

Graph.prototype.sources = function () {
  var self = this
  return _.filter(this.nodes(), function (v) {
    return _.isEmpty(self._in[v])
  })
}

Graph.prototype.sinks = function () {
  var self = this
  return _.filter(this.nodes(), function (v) {
    return _.isEmpty(self._out[v])
  })
}

Graph.prototype.setNodes = function (vs, value) {
  var args = arguments
  var self = this
  _.each(vs, function (v) {
    if (args.length > 1) {
      self.setNode(v, value)
    } else {
      self.setNode(v)
    }
  })
  return this
}

Graph.prototype.setNode = function (v, value) {
  if (_.has(this._nodes, v)) {
    if (arguments.length > 1) {
      this._nodes[v] = value
    }
    return this
  }

  this._nodes[v] = arguments.length > 1 ? value : this._defaultNodeLabelFn(v)
  if (this._isCompound) {
    this._parent[v] = GRAPH_NODE
    this._children[v] = {}
    this._children[GRAPH_NODE][v] = true
  }
  this._in[v] = {}
  this._preds[v] = {}
  this._out[v] = {}
  this._sucs[v] = {}
  ++this._nodeCount
  return this
}

Graph.prototype.node = function (v) {
  return this._nodes[v]
}

Graph.prototype.hasNode = function (v) {
  return _.has(this._nodes, v)
}

Graph.prototype.removeNode = function (v) {
  var self = this
  if (_.has(this._nodes, v)) {
    var removeEdge = function (e) { self.removeEdge(self._edgeObjs[e]) }
    delete this._nodes[v]
    if (this._isCompound) {
      this._removeFromParentsChildList(v)
      delete this._parent[v]
      _.each(this.children(v), function (child) {
        self.setParent(child)
      })
      delete this._children[v]
    }
    _.each(_.keys(this._in[v]), removeEdge)
    delete this._in[v]
    delete this._preds[v]
    _.each(_.keys(this._out[v]), removeEdge)
    delete this._out[v]
    delete this._sucs[v]
    --this._nodeCount
  }
  return this
}

Graph.prototype.setParent = function (v, parent) {
  if (!this._isCompound) {
    throw new Error('Cannot set parent in a non-compound graph')
  }

  if (_.isUndefined(parent)) {
    parent = GRAPH_NODE
  } else {
    // Coerce parent to string
    parent += ''
    for (var ancestor = parent;
      !_.isUndefined(ancestor);
      ancestor = this.parent(ancestor)) {
      if (ancestor === v) {
        throw new Error('Setting ' + parent + ' as parent of ' + v +
                        ' would create a cycle')
      }
    }

    this.setNode(parent)
  }

  this.setNode(v)
  this._removeFromParentsChildList(v)
  this._parent[v] = parent
  this._children[parent][v] = true
  return this
}

Graph.prototype._removeFromParentsChildList = function (v) {
  delete this._children[this._parent[v]][v]
}

Graph.prototype.parent = function (v) {
  if (this._isCompound) {
    var parent = this._parent[v]
    if (parent !== GRAPH_NODE) {
      return parent
    }
  }
}

Graph.prototype.children = function (v) {
  if (_.isUndefined(v)) {
    v = GRAPH_NODE
  }

  if (this._isCompound) {
    var children = this._children[v]
    if (children) {
      return _.keys(children)
    }
  } else if (v === GRAPH_NODE) {
    return this.nodes()
  } else if (this.hasNode(v)) {
    return []
  }
}

Graph.prototype.predecessors = function (v) {
  var predsV = this._preds[v]
  if (predsV) {
    return _.keys(predsV)
  }
}

Graph.prototype.successors = function (v) {
  var sucsV = this._sucs[v]
  if (sucsV) {
    return _.keys(sucsV)
  }
}

Graph.prototype.neighbors = function (v) {
  var preds = this.predecessors(v)
  if (preds) {
    return _.union(preds, this.successors(v))
  }
}

Graph.prototype.isLeaf = function (v) {
  var neighbors
  if (this.isDirected()) {
    neighbors = this.successors(v)
  } else {
    neighbors = this.neighbors(v)
  }
  return neighbors.length === 0
}

Graph.prototype.filterNodes = function (filter) {
  var copy = new this.constructor({
    directed: this._isDirected,
    multigraph: this._isMultigraph,
    compound: this._isCompound
  })

  copy.setGraph(this.graph())

  var self = this
  _.each(this._nodes, function (value, v) {
    if (filter(v)) {
      copy.setNode(v, value)
    }
  })

  _.each(this._edgeObjs, function (e) {
    if (copy.hasNode(e.v) && copy.hasNode(e.w)) {
      copy.setEdge(e, self.edge(e))
    }
  })

  var parents = {}
  function findParent (v) {
    var parent = self.parent(v)
    if (parent === undefined || copy.hasNode(parent)) {
      parents[v] = parent
      return parent
    } else if (parent in parents) {
      return parents[parent]
    } else {
      return findParent(parent)
    }
  }

  if (this._isCompound) {
    _.each(copy.nodes(), function (v) {
      copy.setParent(v, findParent(v))
    })
  }

  return copy
}

/* === Edge functions ========== */

Graph.prototype.setDefaultEdgeLabel = function (newDefault) {
  if (!_.isFunction(newDefault)) {
    newDefault = _.constant(newDefault)
  }
  this._defaultEdgeLabelFn = newDefault
  return this
}

Graph.prototype.edgeCount = function () {
  return this._edgeCount
}

Graph.prototype.edges = function () {
  return _.values(this._edgeObjs)
}

Graph.prototype.setPath = function (vs, value) {
  const self = this
  const args = arguments
  _.reduce(vs, function (v, w) {
    if (args.length > 1) {
      self.setEdge(v, w, value)
    } else {
      self.setEdge(v, w)
    }
    return w
  })
  return this
}

/*
 * setEdge(v, w, [value, [name]])
 * setEdge({ v, w, [name] }, [value])
 */
Graph.prototype.setEdge = function () {
  let v, w, name, value
  let valueSpecified = false
  const arg0 = arguments[0]

  if (typeof arg0 === 'object' && arg0 !== null && 'v' in arg0) {
    v = arg0.v
    w = arg0.w
    name = arg0.name
    if (arguments.length === 2) {
      value = arguments[1]
      valueSpecified = true
    }
  } else {
    v = arg0
    w = arguments[1]
    name = arguments[3]
    if (arguments.length > 2) {
      value = arguments[2]
      valueSpecified = true
    }
  }

  v = '' + v
  w = '' + w
  if (!_.isUndefined(name)) {
    name = '' + name
  }

  var e = edgeArgsToId(this._isDirected, v, w, name)
  if (_.has(this._edgeLabels, e)) {
    if (valueSpecified) {
      this._edgeLabels[e] = value
    }
    return this
  }

  if (!_.isUndefined(name) && !this._isMultigraph) {
    throw new Error('Cannot set a named edge when isMultigraph = false')
  }

  // It didn't exist, so we need to create it.
  // First ensure the nodes exist.
  this.setNode(v)
  this.setNode(w)

  this._edgeLabels[e] = valueSpecified ? value : this._defaultEdgeLabelFn(v, w, name)

  var edgeObj = edgeArgsToObj(this._isDirected, v, w, name)
  // Ensure we add undirected edges in a consistent way.
  v = edgeObj.v
  w = edgeObj.w

  Object.freeze(edgeObj)
  this._edgeObjs[e] = edgeObj
  incrementOrInitEntry(this._preds[w], v)
  incrementOrInitEntry(this._sucs[v], w)
  this._in[w][e] = edgeObj
  this._out[v][e] = edgeObj
  this._edgeCount++
  return this
}

Graph.prototype.edge = function (v, w, name) {
  var e = (arguments.length === 1
    ? edgeObjToId(this._isDirected, arguments[0])
    : edgeArgsToId(this._isDirected, v, w, name))
  return this._edgeLabels[e]
}

Graph.prototype.hasEdge = function (v, w, name) {
  var e = (arguments.length === 1
    ? edgeObjToId(this._isDirected, arguments[0])
    : edgeArgsToId(this._isDirected, v, w, name))
  return _.has(this._edgeLabels, e)
}

Graph.prototype.removeEdge = function (v, w, name) {
  const e = (arguments.length === 1
    ? edgeObjToId(this._isDirected, arguments[0])
    : edgeArgsToId(this._isDirected, v, w, name))
  const edge = this._edgeObjs[e]
  if (edge) {
    v = edge.v
    w = edge.w
    delete this._edgeLabels[e]
    delete this._edgeObjs[e]
    decrementOrRemoveEntry(this._preds[w], v)
    decrementOrRemoveEntry(this._sucs[v], w)
    delete this._in[w][e]
    delete this._out[v][e]
    this._edgeCount--
  }
  return this
}

Graph.prototype.inEdges = function (v, u) {
  var inV = this._in[v]
  if (inV) {
    var edges = _.values(inV)
    if (!u) {
      return edges
    }
    return _.filter(edges, function (edge) { return edge.v === u })
  }
}

Graph.prototype.outEdges = function (v, w) {
  var outV = this._out[v]
  if (outV) {
    var edges = _.values(outV)
    if (!w) {
      return edges
    }
    return _.filter(edges, function (edge) { return edge.w === w })
  }
}

Graph.prototype.nodeEdges = function (v, w) {
  var inEdges = this.inEdges(v, w)
  if (inEdges) {
    return inEdges.concat(this.outEdges(v, w))
  }
}

function incrementOrInitEntry (map, k) {
  if (map[k]) {
    map[k]++
  } else {
    map[k] = 1
  }
}

function decrementOrRemoveEntry (map, k) {
  if (!--map[k]) { delete map[k] }
}

function edgeArgsToId (isDirected, v_, w_, name) {
  var v = '' + v_
  var w = '' + w_
  if (!isDirected && v > w) {
    var tmp = v
    v = w
    w = tmp
  }
  return v + EDGE_KEY_DELIM + w + EDGE_KEY_DELIM +
             (_.isUndefined(name) ? DEFAULT_EDGE_NAME : name)
}

function edgeArgsToObj (isDirected, v_, w_, name) {
  var v = '' + v_
  var w = '' + w_
  if (!isDirected && v > w) {
    var tmp = v
    v = w
    w = tmp
  }
  var edgeObj = { v: v, w: w }
  if (name) {
    edgeObj.name = name
  }
  return edgeObj
}

function edgeObjToId (isDirected, edgeObj) {
  return edgeArgsToId(isDirected, edgeObj.v, edgeObj.w, edgeObj.name)
}

},{"./lodash":18}],17:[function(require,module,exports){
const _ = require('./lodash')
const Graph = require('./graph')

module.exports = {
  write: write,
  read: read
}

function write (g) {
  var json = {
    options: {
      directed: g.isDirected(),
      multigraph: g.isMultigraph(),
      compound: g.isCompound()
    },
    nodes: writeNodes(g),
    edges: writeEdges(g)
  }
  if (!_.isUndefined(g.graph())) {
    json.value = _.clone(g.graph())
  }
  return json
}

function writeNodes (g) {
  return _.map(g.nodes(), function (v) {
    const nodeValue = g.node(v)
    const parent = g.parent(v)
    const node = { v: v }
    if (!_.isUndefined(nodeValue)) {
      node.value = nodeValue
    }
    if (!_.isUndefined(parent)) {
      node.parent = parent
    }
    return node
  })
}

function writeEdges (g) {
  return _.map(g.edges(), function (e) {
    const edgeValue = g.edge(e)
    const edge = { v: e.v, w: e.w }
    if (!_.isUndefined(e.name)) {
      edge.name = e.name
    }
    if (!_.isUndefined(edgeValue)) {
      edge.value = edgeValue
    }
    return edge
  })
}

function read (json) {
  var g = new Graph(json.options).setGraph(json.value)
  _.each(json.nodes, function (entry) {
    g.setNode(entry.v, entry.value)
    if (entry.parent) {
      g.setParent(entry.v, entry.parent)
    }
  })
  _.each(json.edges, function (entry) {
    g.setEdge({ v: entry.v, w: entry.w, name: entry.name }, entry.value)
  })
  return g
}

},{"./graph":16,"./lodash":18}],18:[function(require,module,exports){
/* global window */

var lodash

if (typeof require === 'function') {
  try {
    lodash = require('lodash')
  } catch (e) {}
}

if (!lodash) {
  lodash = window._
}

module.exports = lodash

},{"lodash":undefined}]},{},[1])(1)
});