node-leveldb

node-leveldb

This package provides a simple, lightweight binding for LevelDB to Node.js. LevelDB is an implementation of a log-structured merge-tree that provides fast key-value storage and lookup.

Installation

$ npm install node-leveldb

Documentation

LevelDB

A LevelDB object is constructed and returned when you require('node-leveldb'). This object can be used for all operations on a single LevelDB database.

    var LevelDB = require('node-leveldb');

LevelDB.open(databasePath)

Before operating on a LevelDB object, you have to specify which database those operations apply to. If the specified database doesn't already exist, a new one will be created. If your process doesn't have the necessary permissions to create or open the database, this function will throw an exception.

    LevelDB.open('path/to/my/database');

LevelDB.close()

Closes the database opened by a previous successful call to LevelDB.open(...).

    LevelDB.close();

LevelDB.get(key)

Returns the value associated with key. If key doesn't exist in the database, this function returns null.

    console.log(LevelDB.get('myKey'));

LevelDB.set(key, value)

Inserts data into the database. If there isn't already a value for key in the database, this function creates a new entry and maps key to value. If key already exists, it replaces the old value with value.

    LevelDB.set('Ann Leckie', 'Ancillary Justice');

LevelDB.list([start], [end], callback)

Enumerates data stored in the database. This function takes two optional arguments, the start and end of the range of keys to enumerate. If start is not specified, it is assumed to be from the first item. If end is not specified, it is assumed to be until the last item. Both start and end are inclusive. It's not possible to specify end without first specifying start.

    LevelDB.list('a', 'z', function(key, value) {
        console.log('key: ' + key + ', value: ' + value);
    });

LevelDB.delete(key)

Removes data from the database. If key is found in the database, this function deletes the mapping from key to its value. This function returns true if key was found and a mapping was deleted, false otherwise.

    LevelDB.delete('Ann Leckie');

Example

    var LevelDB = require('node-leveldb');
    LevelDB.open('authors_database');

    LevelDB.set('Frank Herbert', 'Dune');
    LevelDB.set('Ursula K. Le Guin', 'The Left Hand of Darkness');
    LevelDB.set('Larry Niven', 'Ringworld');
    LevelDB.set('Isaac Asimov', 'The Gods Themselves');

    // Print the value associated with 'Frank Herbert'.
    console.log(LevelDB.get('Frank Herbert'));

    LeveLDB.delete('Frank Herbert');

    // Print all items stored in the database.
    LevelDB.list(function(key, value) {
        console.log(key + ': ' + value);
    });

    // Print all items with 'F' <= key <= 'T'.
    LevelDB.list('F', 'T', function(key, value) {
        console.log(key + ': ' + value);
    });

    LevelDB.close();

License

Apache 2.0