node-dijkstra

node-dijkstra

Fast JavaScript implementation of the Dijkstra's shortest path problem for NodeJS

Installation

Since version 2 this plugin uses some ES6 features. You can run the latest version on NodeJS v4.0.0 or newer

npm install node-dijkstra --save

NodeJS prior v4.0.0

On versions of NodeJS prior v4.0.0, although less performant, it's safe to use the version 1.1.3 that you can install as follows:

npm install node-dijkstra@1.1.3 --save

You can then refer to the v1.1.3 documentation

Usage

Basic example:

const Graph = require('node-dijkstra')

const route = new Graph()

route.addNode('A', { B:1 })
route.addNode('B', { A:1, C:2, D: 4 })
route.addNode('C', { B:2, D:1 })
route.addNode('D', { C:1, B:4 })

route.path('A', 'D') // => [ 'A', 'B', 'C', 'D' ]

API

Graph([nodes])

Parameters

• Object|Map nodes optional: Initial nodes graph.

A nodes graph must follow this structure:

{
  node: {
    neighbor: cost Number
  }
}

{
  'A': {
    'B': 1
  },
  'B': {
    'A': 1,
    'C': 2,
    'D': 4
  }
}

Example

const route = new Graph()

// or with pre-populated graph
const route = new Graph({
  'A': { 'B': 1 },
  'B': { 'A': 1, 'C': 2, 'D': 4 }
})

It's possible to pass the constructor a deep Map. This allows using numbers as keys for the nodes.

const graph = new Map()

const a = new Map()
a.set('B', 1)

const b = new Map()
b.set('A', 1)
b.set('C', 2)
b.set('D', 4)

graph.set('A', a)
graph.set('B', b);

const route = new Graph(graph)

Graph#addNode(name, edges)

Add a node to the nodes graph

Parameters

• String name: name of the node
• Object|Map edges: object or Map containing the name of the neighboring nodes and their cost

Returns

Returns this allowing chained calls.

const route = new Graph()

route.addNode('A', { B: 1 })

// chaining is possible
route.addNode('B', { A: 1 }).addNode('C', { A: 3 });

// passing a Map directly is possible
const c = new Map()
c.set('A', 4)

route.addNode('C', c);

Graph#removeNode(name)

Removes a node and all its references from the graph

Parameters

• String name: name of the node to remove

Returns

Returns this allowing chained calls.

const route = new Graph({
  a: { b: 3, c: 10 },
  b: { a: 5, c: 2 },
  c: { b: 1 },
});

route.removeNode('c');
// => The graph now is:
// {
//   a: { b: 3 },
//   b: { a: 5 },
// }

Graph#path(start, goal [, options])

Parameters

• String start: Name of the starting node
• String goal: Name of out goal node
• Object options optional: Addittional options:
  • Boolean trim, default false: If set to true, the result won't include the start and goal nodes
  • Boolean reverse, default false: If set to true, the result will be in reverse order, from goal to start
  • Boolean cost, default false: If set to true, an object will be returned with the following keys:
    • Array path: Computed path (subject to other options)
    • Number cost: Total cost for the found path
  • Array avoid, default []: Nodes to be avoided

Returns

If options.cost is false (default behaviour) an Array will be returned, containing the name of the crossed nodes. By default it will be ordered from start to goal, and those nodes will also be included. This behaviour can be changes with options.trim and options.reverse (see above)

If options.cost is true, an Object with keys path and cost will be returned. path follows the same rules as above and cost is the total cost of the found route between nodes.

When to route can be found, the path will be set to null.

const Graph = require('node-dijkstra')

const route = new Graph()

route.addNode('A', { B: 1 })
route.addNode('B', { A: 1, C: 2, D: 4 })
route.addNode('C', { B: 2, D: 1 })
route.addNode('D', { C: 1, B: 4 })

route.path('A', 'D') // => ['A', 'B', 'C', 'D']

// trimmed
route.path('A', 'D', { trim: true }) // => [B', 'C']

// reversed
route.path('A', 'D', { reverse: true }) // => ['D', 'C', 'B', 'A']

// include the cost
route.path('A', 'D', { cost: true })
// => {
//       path: [ 'A', 'B', 'C', 'D' ],
//       cost: 4
//    }

Upgrading from v1

• The v2 release in not compatible with NodeJS prior to the version 4.0
• The method Graph#shortestPath has been deprecated, use Graph#path instead
• The method Graph#addVertex has been deprecated, use Graph#addNode instead

Testing

npm test