Trying to come up with API for graph traversal. API delays calculation of actual traversal as much as it can. That is, you do not actually starting graph traversal, until you call forEach() method.

0.nodes.js

// How to get all nodes?
traverse(graph)
  .nodes()
  .forEach(function(node) {
    // node is here
  });

// how to get all neighbors of startNodeId?
var grandChildren = traverse(graph)
  .nodes()
  .neighbors(startNodeId)
  .forEach(function(node) {
     // node is here
  });

1. links.js

// let's say you have graph 'graph'.

// How to traverse all links?
traverse(graph)
    .links()
    .forEach(function(link){
      // link has 'to' and 'from' properties 
    });

// How to get all links from node with 'startNodeId'?
traverse(graph)
    .links()
    .from(startNodeId)
    .forEach(function(link){
      // link has 'to' and 'from' properties 
    });

// How to get all links to node with 'toNodeId'?
traverse(graph)
    .links()
    .to(toNodeId)
    .forEach(function(link){
      // link has 'to' and 'from' properties 
    });

2. composite.js

// from()/to()/neighborsOf() can also accept traversers.
// E.g. how to get all neighbors of node's neighbors?

var graphNodes = traverse(graph).nodes();
var children = graphNodes.neighbors(startNodeId);
var grandChildren = graphNodes.neighbors(children);

// how to get all links between startNodeId and grandchildren?
traverse(graph)
  .links()
  .from(children)
  .to(grandChildren)
  .forEach(function(link) {
    // get all links from children to grand children of startNode
  });