keymap

keymap is a tool for compacting/expanding keys in an object. Its main use is to process objects before saving them to the database/cache and after retrieving them.

The motivation behind it was to make objects smaller before storing them in a database, such as MongoDB, for example, saving a reasonable amount of disk space.

Installation

As usual, just run npm install keymap.

Usage

var keymap = require('keymap')
  , map = keymap();
 
map.add('foo', 'f').add('bar', 'b');
 
// returns {f : 'foo', b : 'bar'}
map.compact({
  foo : 'foo',
  bar : 'bar'
});

Defining keys

keymap gives you some options as to how to define your keys and abbreviations. The keymap() function accepts one optional argument, which can be either an object containing a key-abbr map (see #add()) or a string with the path to a file containing the mapping (see #import() below).

If you wish to define or key-abbr pairs directly in your code, you may use the #add() method:

// Passing a key-abbr pair to #add()
map
  .add('foo', 'f')
  .add('bar', 'b');
 
map.getAbbr('foo'); //> 'f'
 
 
// Passing an object to #add()
map.add({
  bar : 'b',
  baz : 'bz'
});
 
map.getAbbr('bar'); //> 'b'
map.getKey('bz'); //> 'baz'

Both will have exactly the same result.

If you wish to store your abbreviations in another file, you may use the #import() method to import your key-abbr maps. The #import() method takes a filepath as an argument. The file must be requirable, that is, must work with require(). keymap uses the js-yaml package to make this work with Yaml files.

// Works with json files
map.import(path.join(__dirname, 'keymap.json'));
 
// Works with yaml files
map.import(path.join(__dirname, 'keymap.yml'));
 
// Works with node modules
map.import(path.join(__dirname, 'keymap.js'));

Both #add() and #import() are chainable:

map
  .add('foo', 'f')
  .add('bar', 'b')
  .add('baz', 'bz')
  .import(path.join(__dirname, 'keymap.yml'));

Note that duplicate keys or abbreviations are not allowed and will throw an error if found.

// Duplicate abbreviations are not allowed
map.add('bar', 'b').add('baz', 'b'); //> err
 
// Duplicate keys are not allowed either
map.add('bar', 'b').add('bar', 'b_'); //> err

Abbreviating and expanding your keys

Once your keymap is defined, there are four methods that process your keys and abbreviations:

• 2 abbreviation/compacting methods
• 2 expansion methods

Use #getAbbr() and #getKey() to retrive the abbreviation or the original form of simple strings.

map.add('foo', 'f').add('bar', 'b');
 
map.getAbbr('foo'); //> 'f'
map.getKey('f'); //> 'foo'
 
// They work with dot-separated keys...
map.getAbbr('foo.bar'); //> 'f.b'
map.getKey('f.b'); //> 'foo.bar'
 
// and with an array too.
map.getAbbr(['foo', 'bar']); //> ['f', 'b']
map.getKey(['f', 'b']); //> ['foo', 'bar']

These methods default to the original value if no abbr/key is found:

map.add('foo', 'f');
 
map.getAbbr('foobar'); //> 'foobar'
map.getKey('foobar'); //> 'foobar'

#compact() and #expand() work on entire objects:

map.add({foo : 'f', bar : 'b');
 
map.compact({foo : 'foo', bar : 'bar'}); //> {f : 'foo', b : 'bar}
map.expand({f : 'foo', b : 'bar'}); //> {foo : 'foo', bar : 'bar'}

They will compact/expand keys in nested objects too:

// Objects inside objects
map.compact({foo : {bar : 'baz'}}); //> {f : {b : 'baz'}}
 
// Objects in arrays
map.compact([{foo : 'bar'}]); //> [{f : 'bar'}]

But there's one caveat: it works only with object literals. Any other object will be returned as is.

var now = new Date();
map.compact(now) === now; //> true

Also note that #compact() and #expand() won't have the same behavior as #getAbbr() and #getKeys() when they receive a string. They will NOT try to abbreviate/expand it, returning the original value.

map.add('foo', 'f');
map.getAbbr('foo'); //> 'f'
map.compact('foo'); //> 'foo'
 
map.getKey('f'); //> 'foo'
map.expand('f'); //> 'f'

Contributing

Feel free to submit any patches or report any issues. I'll do my best to check them as quick as possible (in a few days, usually). When submitting a patch, please add your name and link to the author section below.

Issues and patches regarding grammar errors in code comments and docs are welcome as well. : )

Author

Created by Mathias Kretschek (mkretschek).