ngraph.graph-fork

ngraph.graph
============

Graph) data structure for
ngraph.\*. Library implements API to modify graph structure and supports event-driven
notifications when graph changes.


Creating a graph

Create a graph with no edges and no nodes:

`` js
var createGraph = require('ngraph.graph');
var g = createGraph();
`

Growing a graph


The graph g can be grown in two ways. You can add one node at a time:

` js
g.addNode('hello');
g.addNode('world');
`

Now graph g contains two nodes: hello and world. You can also use addLink()
method to grow a graph. Calling this method with nodes which are not present in
the graph creates them:

` js
g.addLink('space', 'bar'); // now graph 'g' has two new nodes: 'space' and 'bar'
`

If nodes already present in the graph 'addLink()' makes them connected:

` js
// Only a link between 'hello' and 'bar' is created. No new nodes.
g.addLink('hello', 'world');
`

$3


The most common and convenient choices are numbers and strings. You can
associate arbitrary data with node via optional second argument of addNode()
method:

` js
// Node 'world' is associated with a string object 'custom data'
g.addNode('world', 'custom data');

// You can associate arbitrary objects with node:
g.addNode('server', {
status: 'on',
ip: '127.0.0.1'
});

// to get data back use data property of node:
var server = g.getNode('server');
console.log(server.data); // prints associated object
`

You can also associate arbitrary object with a link using third optional
argument of addLink() method:

` js
// A link between nodes '1' and '2' is now associated with object 'x'
g.addLink(1, 2, x);
`

$3

After you created a graph one of the most common things to do is to enumerate
its nodes/links to perform an operation.

` js
g.forEachNode(function(node){
console.log(node.id, node.data);
});
`

The function takes callback which accepts current node. Node object may contain
internal information. node.id and node.data represent parameters passed to
the g.addNode(id, data) method and they are guaranteed to be present in future
versions of the library.

To enumerate all links in the graph use forEachLink() method:

` js
g.forEachLink(function(link) {
console.dir(link);
});
`

To enumerate all links for a specific node use forEachLinkedNode() method:
` js
g.forEachLinkedNode('hello', function(linkedNode, link){
console.log("Connected node: ", linkedNode.id, linkedNode.data);
console.dir(link); // link object itself
});
`

This method always enumerates both inbound and outbound links. If you want to
get only outbound links, pass third optional argument:
` js
g.forEachLinkedNode('hello',
function(linkedNode, link) { / ... / },
true // enumerate only outbound links
);
`

To get a particular node object use getNode() method. E.g.:

` js
var world = g.getNode('world'); // returns 'world' node
console.log(world.id, world.data);
`

To get a particular link object use getLink() method:

` js
var helloWorldLink = g.getLink('hello', 'world'); // returns a link from 'hello' to 'world'
console.log(helloWorldLink);
`

To remove a node or a link from a graph use removeNode() or removeLink()
correspondingly:

` js
g.removeNode('space');
// Removing link is a bit harder, since method requires actual link object:
g.forEachLinkedNode('hello', function(linkedNode, link){
g.removeLink(link);
});
`

You can also remove all nodes and links by calling

` js
g.clear();
`

Listening to Events

Whenever someone changes your graph you can listen to notifications:

` js
g.on('changed', function(changes) {
console.dir(changes); // prints array of change records
});

g.add(42); // this will trigger 'changed event'
`

Each change record holds information:

`
ChangeRecord = {
changeType: add|remove|update - describes type of this change
node: - only present when this record reflects a node change, represents actual node
link: - only present when this record reflects a link change, represents actual link
}
`

Sometimes it is desirable to react only on bulk changes. ngraph.graph supports
this via beginUpdate()/endUpdate() methods:

` js
g.beginUpdate();
for(var i = 0; i < 100; ++i) {
g.addLink(i, i + 1); // no events are triggered here
}
g.endUpdate(); // this triggers all listners of 'changed' event
`

If you want to stop listen to events use off() method:
` js
g.off('changed', yourHandler); // no longer interested in changes from graph
`

For more information about events, please follow to ngraph.events

Install
=======

With npm do:

`
npm install ngraph.graph
``

License
=======
BSD 3-clause