if your data looks like this:
```js
var data = {
bedfordshire: 'England',
aberdeenshire: 'Scotland',
buckinghamshire: 'England',
argyllshire: 'Scotland',
bambridgeshire: 'England',
cheshire: 'England',
ayrshire: 'Scotland',
banffshire: 'Scotland'
}
```
you can compress it like this:
```js
import { pack } from 'efrt'
var str = pack(data)
//'England:b0che1;ambridge0edford0uckingham0;shire|Scotland:a0banff1;berdeen0rgyll0yr0;shire'
```
then \_very!\_ quickly flip it back into:
```js
import { unpack } from 'efrt'
var obj = unpack(str)
obj['bedfordshire'] //'England'
```
Yep,
**efrt** packs category-type data into a _[very compressed prefix trie](https://en.wikipedia.org/wiki/Trie)_ format, so that redundancies in the data are shared, and nothing is repeated.
By doing this clever-stuff ahead-of-time, **efrt** lets you ship _much more_ data to the client-side, without hassle or overhead.
The whole library is **8kb**, the unpack half is barely **2kb**.
it is based on:
- 😍 [tamper](https://nytimes.github.io/tamper/) by the [NYTimes](https://github.com/NYTimes/)
- 💝 [lookups](https://github.com/mckoss/lookups) by [Mike Koss](https://github.com/mckoss),
- 💓 [bits.js](http://stevehanov.ca/blog/index.php?id=120) by [Steve Hanov](https://twitter.com/smhanov)
Benchmarks!
- get a js object into very compact form
- reduce filesize/bandwidth a bunch
- ensure the unpacking time is negligible
- keep word-lookups on critical-path
```js
import { pack, unpack } from 'efrt' // const {pack, unpack} = require('efrt')
var foods = {
strawberry: 'fruit',
blueberry: 'fruit',
blackberry: 'fruit',
tomato: ['fruit', 'vegetable'],
cucumber: 'vegetable',
pepper: 'vegetable'
}
var str = pack(foods)
//'{"fruit":"bl0straw1tomato;ack0ue0;berry","vegetable":"cucumb0pepp0tomato;er"}'
var obj = unpack(str)
console.log(obj.tomato)
//['fruit', 'vegetable']
```
---
or, an Array:
if you pass it an array of strings, it just creates an object with `true` values:
```js
const data = [
'january',
'february',
'april',
'june',
'july',
'august',
'september',
'october',
'november',
'december'
]
const packd = pack(data)
// true¦a6dec4febr3j1ma0nov4octo5sept4;rch,y;an1u0;ly,ne;uary;em0;ber;pril,ugust
const sameArray = Object.keys(unpack(packd))
// same thing !
```
## Reserved characters
the keys of the object are normalized. Spaces/unicode are good, but numbers, case-sensitivity, and _some punctuation_ (semicolon, comma, exclamation-mark) are not (yet) supported.
```js
specialChars = new RegExp('[0-9A-Z,;!:|¦]')
```
_efrt_ is built-for, and used heavily in [compromise](https://github.com/nlp-compromise/compromise), to expand the amount of data it can ship onto the client-side.
If you find another use for efrt, please [drop us a line](mailto:spencermountain@gmail.com)🎈
## Performance
_efrt_ is tuned to be very quick to unzip. It is O(1) to lookup. Packing-up the data is the slowest part, which is usually fine:
```js
var compressed = pack(skateboarders) //1k words (on a macbook)
var trie = unpack(compressed)
// unpacking-step: 5.1ms
trie.hasOwnProperty('tony hawk')
// cached-lookup: 0.02ms
```
## Size
`efrt` will pack filesize down as much as possible, depending upon the redundancy of the prefixes/suffixes in the words, and the size of the list.
- list of countries - `1.5k -> 0.8k` _(46% compressed)_
- all adverbs in wordnet - `58k -> 24k` _(58% compressed)_
- all adjectives in wordnet - `265k -> 99k` _(62% compressed)_
- all nouns in wordnet - `1,775k -> 692k` _(61% compressed)_
but there are some things to consider:
- bigger files compress further (see [🎈 birthday problem](https://en.wikipedia.org/wiki/Birthday_problem))
- using efrt will reduce gains from gzip compression, which most webservers quietly use
- english is more suffix-redundant than prefix-redundant, so non-english words may benefit from other styles
Assuming your data has a low _category-to-data ratio_, you will hit-breakeven with at about 250 keys. If your data is in the thousands, you can very be confident about saving your users some considerable bandwidth.
## Use
**IE9+**
```html
```
if you're doing the second step in the client, you can load just the CJS unpack-half of the library(~3k):
```js
const unpack = require('efrt/unpack') // node/cjs
```
```html
```
Thanks to [John Resig](https://johnresig.com/) for his fun [trie-compression post](https://johnresig.com/blog/javascript-trie-performance-analysis/) on his blog, and [Wiktor Jakubczyc](https://github.com/monolithpl) for his performance analysis work
MIT
