topological-sort/README.md

Topological sort

# Topological sort

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This package is distributed as Javascript, but you can also use it in your TypeScript project.

## API
### Javascript example

```javascript
const { TopologicalSort } = require('topological-sort');

// you can pass nodes as a map into constructor:
const nodes = new Map();
nodes.set('variables', variablesObj);
nodes.set('mixins', mixinsObj);
const sortOp = new TopologicalSort(nodes);

// ...or add them to existing object instance with addNode() or addNodes():
sortOp.addNode('block', blocksObj);
sortOp.addNodes(new Map([
    ['block_mod_val1', blockModObj1],
    ['block_mod_val2', blockModObj2]
]));

// then you should add adges between nodes
sortOp.addEdge('variables', 'mixins'); // from, to
sortOp.addEdge('mixins', 'block');
sortOp.addEdge('variables', 'block');
sortOp.addEdge('block', 'block_mod_val2');
sortOp.addEdge('block', 'block_mod_val1');

// sorting is simple: it returns a new map wih sorted elements
// if circular dependency is found, sort() operation throws an AssertionError
const sorted = sortOp.sort();
const sortedKeys = [...sorted.keys()]; // ['variables', 'mixins', 'block', 'block_mod_val1', 'block_mod_val2']

// values of the `sorted` map are objects with this shape: `{ children, node }`
// where node is the node object that you provided
// and children is a map which values have the same shape
const { node: variablesObj, children: variablesChildren } = sorted.get('variables');
const { node: blocksObj1 } = variablesChildren.get('block');
const { node: blocksObj2 } = sorted.get('block');
assert(blocksObj1 === blocksObj2); // true
```

### Typescript example

```typescript
import TopologicalSort from 'topological-sort';

// TopologicalSort class instances have a map inside.
// This map stores the references between your nodes (edges)
// "NodesKeyType" is the type for your tree node identifiers
// "NodesValueType" is the type for your tree nodes
const nodes = new Map<NodesKeyType, NodesValueType>();
nodes.set('variables', variablesObj);
nodes.set('mixins', mixinsObj);
const sortOp = new TopologicalSort<NodesKeyType, NodesValueType>(nodes);

// `sortedKeys` is a topologically sorted list of node keys
sortOp.addEdge('variables', 'mixins');
const sorted = sortOp.sort();
const sortedKeys = [...sorted.keys()]; // ['variables', 'mixins']

// `sorted` contains all nodes and their children
const { node: variablesObj, children: variablesChildren } = sorted.get('variables');
const { node: blocksObj1 } = variablesChildren.get('block');
const { node: blocksObj2 } = sorted.get('block');
assert(blocksObj1 === blocksObj2); // true
```

## More info:

 * https://en.wikipedia.org/wiki/Topological_sorting
 * https://www.cs.usfca.edu/~galles/visualization/TopoSortDFS.html
 * http://www.geeksforgeeks.org/topological-sorting/
 * https://www.youtube.com/watch?v=ddTC4Zovtbc