forked from lix-project/lix-website
79 lines
3.7 KiB
Markdown
79 lines
3.7 KiB
Markdown
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# Dependency Graph
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Simple dependency graph
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## Overview
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This is a simple dependency graph useful for determining the order to do a list of things that depend on certain items being done before they are.
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To use, `npm install dependency-graph` and then `require('dependency-graph').DepGraph`
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## API
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### DepGraph
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Nodes in the graph are just simple strings with optional data associated with them.
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- `addNode(name, data)` - add a node in the graph with optional data. If `data` is not given, `name` will be used as data
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- `removeNode(name)` - remove a node from the graph
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- `hasNode(name)` - check if a node exists in the graph
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- `size()` - return the number of nodes in the graph
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- `getNodeData(name)` - get the data associated with a node (will throw an `Error` if the node does not exist)
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- `setNodeData(name, data)` - set the data for an existing node (will throw an `Error` if the node does not exist)
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- `addDependency(from, to)` - add a dependency between two nodes (will throw an `Error` if one of the nodes does not exist)
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- `removeDependency(from, to)` - remove a dependency between two nodes
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- `clone()` - return a clone of the graph. Any data attached to the nodes will only be *shallow-copied*
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- `dependenciesOf(name, leavesOnly)` - get an array containing the nodes that the specified node depends on (transitively). If `leavesOnly` is true, only nodes that do not depend on any other nodes will be returned in the array.
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- `dependantsOf(name, leavesOnly)` (aliased as `dependentsOf`) - get an array containing the nodes that depend on the specified node (transitively). If `leavesOnly` is true, only nodes that do not have any dependants will be returned in the array.
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- `directDependenciesOf(name)` - get an array containing the direct dependencies of the specified node
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- `directDependantsOf(name)` (aliased as `directDependentsOf`) - get an array containing the nodes that directly depend on the specified node
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- `overallOrder(leavesOnly)` - construct the overall processing order for the dependency graph. If `leavesOnly` is true, only nodes that do not depend on any other nodes will be returned.
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- `entryNodes()` - array of nodes that have no dependants (i.e. nothing depends on them).
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Dependency Cycles are detected when running `dependenciesOf`, `dependantsOf`, and `overallOrder` and if one is found, a `DepGraphCycleError` will be thrown that includes what the cycle was in the message as well as the `cyclePath` property: e.g. `Dependency Cycle Found: a -> b -> c -> a`. If you wish to silence this error, pass `circular: true` when instantiating `DepGraph` (more below).
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## Examples
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var DepGraph = require('dependency-graph').DepGraph;
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var graph = new DepGraph();
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graph.addNode('a');
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graph.addNode('b');
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graph.addNode('c');
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graph.size() // 3
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graph.addDependency('a', 'b');
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graph.addDependency('b', 'c');
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graph.dependenciesOf('a'); // ['c', 'b']
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graph.dependenciesOf('b'); // ['c']
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graph.dependantsOf('c'); // ['a', 'b']
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graph.overallOrder(); // ['c', 'b', 'a']
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graph.overallOrder(true); // ['c']
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graph.entryNodes(); // ['a']
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graph.addNode('d', 'data');
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graph.getNodeData('d'); // 'data'
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graph.setNodeData('d', 'newData');
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graph.getNodeData('d'); // 'newData'
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var circularGraph = new DepGraph({ circular: true });
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circularGraph.addNode('a');
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circularGraph.addNode('b');
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circularGraph.addNode('c');
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circularGraph.addNode('d');
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circularGraph.addDependency('a', 'b');
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circularGraph.addDependency('b', 'c'); // b depends on c
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circularGraph.addDependency('c', 'a'); // c depends on a, which depends on b
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circularGraph.addDependency('d', 'a');
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circularGraph.dependenciesOf('b'); // ['a', 'c']
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circularGraph.overallOrder(); // ['c', 'b', 'a', 'd']
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