@baileyherbert/dependency-graph

Dependency Graph

This package contains a simple and modern dependency graph data structure for TypeScript.

npm install @baileyherbert/dependency-graph

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• Example
• Constructor
• Methods
  • addNode(node, [data])
  • removeNode(node)
  • hasNode(node)
  • getNodeData(node)
  • setNodeData(node, [data])
  • hasNodeData(node)
  • addDependency(from, to)
  • removeDependency(from, to)
  • getDirectDependenciesOf(node)
  • getDirectDependentsOf(node)
  • getDependenciesOf(node, [leaves])
  • getDependentsOf(node, [leaves])
  • getOverallOrder([leaves])
  • getEntryNodes()
  • clone()
  • clear()
• Properties
  • allowCircularDependencies
  • size
• Circular dependencies

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Example

import { DependencyGraph } from '@baileyherbert/dependency-graph';

const graph = new DependencyGraph<string>();

graph.addNode('a');
graph.addNode('b');
graph.addNode('c');

graph.addDependency('a', 'b');
graph.addDependency('b', 'c');

graph.getDependenciesOf('a');  // ['c', 'b']
graph.getDependenciesOf('b');  // ['c']

graph.getDependentsOf('c');    // ['a', 'b']

graph.getOverallOrder();       // ['c', 'b', 'a']
graph.getOverallOrder(true);   // ['c']

graph.addNode('d', 'data');
graph.setNodeData('c', 'more data');

graph.getNodeData('d');        // 'data'
graph.getNodeData('c');        // 'more data'
graph.getNodeData('b');        // undefined

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Constructor

new DependencyGraph<T>()
new DependencyGraph<T, D>()

• <T> is the type to use for nodes.
• <D> is the type to use for node data. Defaults to any.

Methods

addNode(node, [data])

Adds a node to the dependency graph.

Returns: void
Parameters:

• node: T – The node to add.
• data?: D – Optional data to associate with this node.

removeNode(node)

Removes a node from the dependency graph.

Returns: void
Parameters:

• node: T – The node to remove.

hasNode(node)

Returns true if the specified node exists in the graph.

Returns: boolean
Parameters:

• node: T – The node to check for.

getNodeData(node)

Returns the data for the specified node or undefined if not available.

Returns: D | undefined
Parameters:

• node: T – The node to retrieve data for.

setNodeData(node, [data])

Sets the data for the specified node. Setting the data to undefined will remove it.

Returns: void
Parameters:

• node: T – The node to set data for.
• data?: D – Optional data to associate with this node.

hasNodeData(node)

Returns true if the node has associated data.

Returns: boolean
Parameters:

• node: T – The node to check for.

addDependency(from, to)

Registers that the from node depends on the to node.

Returns: void
Parameters:

• from: T – The dependent node.
• to: T – The dependency node.

removeDependency(from, to)

Removes a dependency between two nodes. The given from node will no longer be dependent upon the to node.

Returns: void
Parameters:

• from: T – The dependent node.
• to: T – The dependency node.

getDirectDependenciesOf(node)

Returns an array containing all direct dependencies of the given node.

Returns: T[]
Parameters:

• node: T – The node to check for.

getDirectDependentsOf(node)

Returns an array containing the nodes that directly depend on the given node.

Returns: T[]
Parameters:

• node: T – The node to check for.

getDependenciesOf(node, [leaves])

Returns an array containing the nodes that the specified node depends on (transitively).

Returns: T[]
Parameters:

• node: T – The node to check for.
• leaves: boolean – Only return leaves. Defaults to false.

getDependentsOf(node, [leaves])

Returns an array containing the nodes that depend on the specified node (transitively).

Returns: T[]
Parameters:

• node: T – The node to check for.
• leaves: boolean – Only return leaves. Defaults to false.

getOverallOrder([leaves])

Computes the overall processing order for the dependency graph. Throws an error if circular dependencies are detected.

Returns: T[]
Parameters:

• leaves: boolean – Only return leaves. Defaults to false.

getEntryNodes()

Returns an array of nodes that have no dependents.

Returns: T[]

clone()

Creates a copy of the dependency graph.

Returns: DependencyGraph<T, D>

clear()

Clears all nodes and data from the dependency graph.

Returns: void

Properties

allowCircularDependencies

Whether or not circular dependencies are allowed. Defaults to false in which case errors will be thrown upon their detection.

Type: boolean
Default: false

size

The number of nodes in the graph.

Type: number (read-only)

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Circular dependencies

When circular dependencies occur and allowCircularDependencies is false, an error will be thrown. You can catch this error and use the information within it to determine which nodes are responsible.

import { CircularDependencyError } from '@baileyherbert/dependency-graph';

try {
	// Implement graph with a circular dependency
	graph.addDependency('a', 'b');
	graph.addDependency('b', 'c');
	graph.addDependency('c', 'a');

	// The error will be thrown when running computations
	graph.getOverallOrder();
}
catch (error) {
	if (error instanceof CircularDependencyError) {
		error.path;     // ['a', 'b', 'c', 'a']
		error.node;     // 'a'
		error.message;  // Detected circular dependencies (a -> b -> c -> a)
	}
}