graph-traversal

Gremlin-like generalized graph traversal API

Usage

This package comes in iterable and async iterable flavors. The exports are named the same in each.

import { VertexTraversal, EdgeTraversal } from "graph-traversal"
import { VertexTraversal, EdgeTraversal } from "graph-traversal/async"

Currently, the only way to begin a traversal is to call VertexTraversal.from. Any graph with a match method will be accepted. (Implementers can always make a proxy object that implements such.)

Almost all traversal methods yield a new traversal object that holds immutable state.

For the below method descriptions:

• in means traveling towards the current result.
• out means traveling away from the current result.
• both means getting results from both in and out directions.
• For the methods with optional parameters: undefined can be a valid vertex, so passing undefined is not the same as passing no arguments at all. Passing undefined will match undefined vertices or edges with the graph.

Common traversal methods

traversal.as(key)

Assigns a key name to the current object being traversed. For a vertex traversal, the object will be a vertex. For an edge traversal, the object will be an edge.

The key can be a string, a number, or a symbol.

traversal.collect()

Collects all of the named objects as a single object. For example, .as("foo").out("child").as("bar") will emit objects with the signature { foo: ?, bar: ? }.

traversal.filter(filterFn)

Filters the currently matched vertices/edges.

traversal.filterTriple(filterFn)

Filters the previously matched triple. For example, .out("x").filterTriple(fn) will consider all the triples that led to x. Note: At the beginning of the traversal, there will be no triples.

traversalSymbol.iterator or traversalSymbol.asyncIterator

Traverses through the currently matched vertices or edges.

Vertex traversal methods

VertexTraversal.from(graph, vertex)

Creates a new vertex traversal starting from the specified vertex.

graph should be an object that implements a match method that takes pattern. pattern is an object that has any of the keys subject, predicate, or object. match should return either an IterableIterator or an AsyncIterableIterator, depending on the flavor of traversal, that iterates through all of the triples matched by the pattern.

vt.out(), vt.in(), vt.both()

out, in, and both can take the following arguments:

• () - go through all the adjacent vertices in the specified direction
• (predicate: E) - filter by predicate
• (predicate: E, vertex: V) - filter by predicate and adjacent vertex

Return value: vertex traversal

vt.outE(), vt.inE(), vt.bothE()

outE, inE, and bothE can take the following arguments:

• () - go through all the adjacent edges
• (predicate: E) - filter by predicate

Return value: edge traversal

Edge traversal methods

et.outV(), et.inV(), et.bothV()

outV, inV, and bothV depend on the last set of triples matched. There will be no previous triples at the start of the traversal

They can take the following arguments:

• () - go through all the adjacent vertices in the specified direction
• (vertex: V) - filter by vertex

Return value: vertex traversal