toposort

What is toposort?

The toposort npm package is used for sorting directed acyclic graphs (DAG) into a topological order. It is useful for tasks where dependencies need to be resolved in a specific sequence, such as task scheduling, resolving package dependencies, or processing data with dependencies.

What are toposort's main functionalities?

Topological sorting

This feature allows you to sort a list of edges representing dependencies into a topological order. The edges are pairs where the first element depends on the second one.

const toposort = require('toposort');
const edges = [
  ['task1', 'task2'],
  ['task2', 'task3'],
  ['task3', 'task4']
];
const sorted = toposort(edges);
console.log(sorted); // ['task1', 'task2', 'task3', 'task4']

Other packages similar to toposort

dagre

Dagre is a JavaScript library that lays out directed graphs on the client-side. While toposort focuses on sorting nodes in a topological order, dagre provides the additional functionality of graph layout for visualization purposes.

graphlib

Graphlib is a library that provides data structures for undirected and directed multi-graphs along with algorithms to use with them. It includes topological sorting as well as other algorithms like shortest path. It is more comprehensive than toposort, which is specialized for topological sorting.

dependency-graph

Dependency-graph is a simple dependency graph library that can be used to handle and sort dependencies. It offers a higher-level API compared to toposort, allowing for the addition of nodes and dependencies in a more object-oriented manner.

README

Toposort

Sort directed acyclic graphs

Installation

npm install toposort or component install marcelklehr/toposort

then in your code:

toposort = require('toposort')

Usage

We want to sort the following graph.

// First, we define our edges.
var graph = [
  ['put on your shoes', 'tie your shoes']
, ['put on your shirt', 'put on your jacket']
, ['put on your shorts', 'put on your jacket']
, ['put on your shorts', 'put on your shoes']
]


// Now, sort the vertices topologically, to reveal a legal execution order.
toposort(graph)
// [ 'put on your shirt'
// , 'put on your shorts'
// , 'put on your jacket'
// , 'put on your shoes'
// , 'tie your shoes' ]

(Note that there is no defined order for graph parts that are not connected -- you could also put on your jacket after having tied your shoes...)

Sorting dependencies

It is usually more convenient to specify dependencies instead of "sequences".

// This time, edges represent dependencies.
var graph = [
  ['tie your shoes', 'put on your shoes']
, ['put on your jacket', 'put on your shirt']
, ['put on your shoes', 'put on your shorts']
, ['put on your jacket', 'put on your shorts']
]

toposort(graph) 
// [ 'tie your shoes'
// , 'put on your shoes'
// , 'put on your jacket'
// , 'put on your shirt'
// , 'put on your shorts' ]

// Now, reversing the list will reveal a legal execution order.
toposort(graph).reverse() 
// [ 'put on your shorts'
// , 'put on your shirt'
// , 'put on your jacket'
// , 'put on your shoes'
// , 'tie your shoes' ]

API

toposort(edges)

• edges {Array} An array of directed edges describing a graph. An edge looks like this: [node1, node2] (vertices needn't be strings but can be of any type).

Returns: {Array} a list of vertices, sorted from "start" to "end"

Throws an error if there are any cycles in the graph.

toposort.array(nodes, edges)

• nodes {Array} An array of nodes
• edges {Array} An array of directed edges. You don't need to mention all nodes here.

This is a convenience method that allows you to define nodes that may or may not be connected to any other nodes. The ordering of unconnected nodes is not defined.

Returns: {Array} a list of vertices, sorted from "start" to "end"

Throws an error if there are any cycles in the graph.

Tests

Run the tests with node test.js.

Legal

MIT License