https://github.com/hackergrrl/field-trip

:triangular_flag_on_post: Walk an unknown directed graph async
https://github.com/hackergrrl/field-trip

Last synced: 20 days ago
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:triangular_flag_on_post: Walk an unknown directed graph async

• Host: GitHub
• URL: https://github.com/hackergrrl/field-trip
• Owner: hackergrrl
• Created: 2016-06-07T18:48:28.000Z (over 8 years ago)
• Default Branch: master
• Last Pushed: 2016-09-07T21:06:13.000Z (about 8 years ago)
• Last Synced: 2024-10-24T10:11:38.465Z (27 days ago)
• Language: JavaScript
• Homepage:
• Size: 5.86 KB
• Stars: 4
• Watchers: 2
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# field-trip

> walk a directed graph async without knowing its structure ahead of time

## Background

There are plenty of modules for traversing

1. file systems

2. arrays

3. trees

so long as their structure is known ahead of time. What if you require the asynchronous

process of visiting a node in order to learn of its children?

## Usage

Let's take a field trip through a tree, pretending to be ignorant of its

structure up front:

```js

var fieldtrip = require('field-trip')

var db = {}

db[0] = {key: 0, value: 1, kids: []}

db[1] = {key: 1, value: 2, kids: [0]}

db[2] = {key: 2, value: 3, kids: [4]}

db[3] = {key: 3, value: 4, kids: [2]}

db[4] = {key: 4, value: -1, kids: [0, 1]}

// Begin taking a field trip through this unknown structure!

fieldtrip([3], visit, function () {

  console.log('all done')

})

// Visit a single node. 'add' to add children; 'done' when finished visting.

function visit (key, add, done) {

  lookupKey(key, function (err, node) {

    if (err) return done(err)

    console.log('KEY', key, 'VALUE', node.value)

    node.kids.forEach(add)

    done()

  })

}

// Look up a key through some intensive asynchronous process.

function lookupKey (key, cb) {

  setTimeout(function () {

    cb(null, db[key])

  }, Math.floor(Math.random() * 100))

}

```

This will output

```

KEY 3 VALUE 4

KEY 2 VALUE 3

KEY 4 VALUE -1

KEY 0 VALUE 1

KEY 1 VALUE 2

KEY 0 VALUE 1

all done

```

## API

```js

var fieldtrip = require('field-trip')

```

### fieldtrip(origins, visit, finish)

Calls the function `visit` on each element in the array `origins`.

Each call to visit expects the signature `function (node, add, done)`, where

`add` can be called with another node to visit, and `done` **MUST** be called to

signal that this node's visitation has completed. Call `done(err)` to signal an

error and end the traversal.

`finish` is called when either all nodes have been visited, or an error has

occurred.

## Install

With [npm](https://npmjs.org/) installed, run

```

$ npm install field-trip

```

## See Also

If you use [pull-streams](https://pull-stream.github.io/), consider

[pull-traverse](https://github.com/pull-stream/pull-traverse) as an excellent

alternative.

## Thanks!

Thanks to chrisdickenson's

[walk-dag](https://github.com/chrisdickinson/walk-dag) module, which was the

closest I could find to this. Example and tests are mostly stolen from his work.

:)

## License

ISC