# level-track

> receive updates from a set of keys and ranges in leveldb

Latest version **0.1.0** (published 2013-09-07) · MIT license · 0 weekly downloads

## Install

```sh
npm install level-track
pnpm add level-track
yarn add level-track
bun add level-track
```

## Health

**Score 15/100 (F)** — status: abandoned.

Positive: no vulnerabilities.

Warnings: low downloads; no types; no esm support; pre 1.0.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 0.1.0 |
| Published | 2013-09-07 |
| First published | 2013-09-05 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | CommonJS |
| Dependencies | 3 |
| Known vulnerabilities | 0 |
| Install scripts | no |
| Author | James Halliday |
| Maintainers | substack |
| Keywords | level, subscribe, database, live, updating, range, query |

## Links

- npm: https://www.npmjs.com/package/level-track
- Repository: https://github.com/substack/level-track
- Issues: https://github.com/substack/level-track/issues
- npm.io page: https://npm.io/package/level-track

## Dependencies (3)

- [split](https://npm.io/package/split.md) ~0.2.10
- [through](https://npm.io/package/through.md) ~2.3.4
- [stream-combiner](https://npm.io/package/stream-combiner.md) ~0.0.2

## Recent versions

- 0.1.0 (latest) — 2013-09-07
- 0.0.0 — 2013-09-05

## README

# level-track

keep track of all the active queries from a request to route live updates

[![build status](https://secure.travis-ci.org/substack/level-track.png)](http://travis-ci.org/substack/level-track)

# example

In this example we'll subscribe to the range of keys `"f"` through `"p"` and the
singular key `"c"`. The database is then populated with random keys and values
to show that only keys `"f"` through `"p"` inclusive and `"c"` are captured.

``` js
var sub = require('level-sublevel');
var db = sub(require('level')('test.db'));
var tracker = require('level-track')(db);
var through = require('through');

var t = tracker();
t.pipe(process.stdout);

t.write('"c"\n');
t.write('["f","p"]\n');

setInterval(function () {
    var l = Math.floor(Math.random() * 2) + 1;
    var key = '';
    for (var i = 0; i < l; i++) {
        key += String.fromCharCode(Math.random() * 26 + 97);
    }
    db.put(key, { n: Math.floor(Math.random() * 100) });
}, 250);
```

output:

```
{"type":"put","key":"jr","value":{"n":92}}
{"type":"put","key":"ft","value":{"n":41}}
{"type":"put","key":"g","value":{"n":32}}
{"type":"put","key":"c","value":{"n":55}}
{"type":"put","key":"kh","value":{"n":60}}
{"type":"put","key":"m","value":{"n":43}}
{"type":"put","key":"p","value":{"n":40}}
{"type":"put","key":"nc","value":{"n":64}}
{"type":"put","key":"l","value":{"n":70}}
{"type":"put","key":"fy","value":{"n":41}}
{"type":"put","key":"kp","value":{"n":98}}
{"type":"put","key":"mk","value":{"n":48}}
{"type":"put","key":"h","value":{"n":27}}
^C
```

# protocol

The tracking protocol is newline-delimited json.
Each line should match one of these formats:

## "key"

Receive updates from a single key.

## ["startkey","endkey"]

Receive updates from the range `"startkey"` through `"endkey"`, inclusive.

## ["startkey","endkey","sincekey"]

Receive updates from the range `"startkey"` through `"endkey"`, inclusive and
populate the result stream with data from the exclusive `"sincekey"` through
`"endkey"`.

This form is useful so that no updates slip past due to delays from rendering
the initial content and establishing a live connection.

# methods

``` js
var tracker = require('level-track')
```

## var t = tracker(opts)

Return a duplex stream that expects 
input of the form documented in the protocol section and produces output of the
form:

``` json
{"type":"put","key":"h","value":{"n":27}}
```

which is the same format that `db.hooks` and `db.batch()` use.

When `opts.objectMode` is true, output is written as objects. Otherwise, output
is written as newline-delimited lines of json.

You may also specify an optional `opts.keyMap(key)` function to pre-transform
keys. Return the value you want to use for the key.

# install

With [npm](https://npmjs.org) do:

```
npm install level-tracker
```

# license

MIT

---
_Source: https://npm.io/package/level-track · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._