Simple datastore

A simplistic redis clone, whereby it stores key-value pairs and is accessible programmatically, or via the provided CLI.

CLI Commands

SET <key> <value>

Sets a particular key to the specified value in the datastore.

> SET x 10
> GET x
10

GET <key>

Retrieves the specified key's value.

> SET x 10
> GET x
10

UNSET <key>

Deletes the specified key.

> SET x 10
> GET x
10
> UNSET x
> GET x
NULL

NUMEQUALTO <value>

Retrieves the number of keys with the specified value.

> SET x 10
> GET x
10
> SET y 10
> NUMEQUALTO 10
2

BEGIN

Starts a new transaction. Transactions can be nested.

> SET x 10
> GET x
10
> BEGIN
> SET x 20
> GET x
20
> ROLLBACK
> GET x
10

COMMIT

Commits the changes made to the datastore.

> SET x 10
> GET x
10
> BEGIN
> SET x 20
> GET x
20
> COMMIT
> GET x
20

ROLLBACK

Undoes any changes made to the datastore during the current transaction.

> SET x 10
> GET x
10
> BEGIN
> SET x 20
> GET x
20
> ROLLBACK
> GET x
10

END

Terminates the CLI and triggers it's end event.

> SET 10
> END
(program terminates)

Datastore Usage

In addition to using the CLI, you can also access the datastore programmatically.

Constructor

Arguments:

None.

Example:

const store = new Datastore();

Methods

set(key, value)

Sets the key to specified value. Will trigger the set event with key, old value, and new value.

Arguments:

1. key (string): The key to set.
2. value (value): The value to associate with the key.

Returns:

Nothing.

Example:

store.set('x', '10');

get(key)

Retrieves the key's associated value.

Arguments:

1. key (string): The key to lookup.

Returns:

(string): The value associated with the key in the store.

Example:

store.set('x', '10');
const result = store.get('x');
console.log(result);
// 10

unset(key)

Deletes the key in the store. Will emit the unset event with key, and key's old value.

Arguments:

1. key (string): The key to delete.

Returns:

Nothing.

Example:

store.set('x', '10');
let result = store.get('x');
console.log(result);
// 10
store.unset('x');
let result = store.get('x');
console.log(result);
// NULL

numEqualTo(value)

Returns a count of the number of keys matching the value specified.

Arguments:

1. value (string): The value to test against.

Returns:

(int): The number of keys that match value;

Example:

store.set('x', '10');
store.set('y', '10');
let result = store.numEqualTo('10');
console.log(result);
// 2

Events

set

Arguments

1. key (string): The key that was set.
2. oldValue (string): The value of key prior to being set.
3. newValue (string): The new value of key.

unset

Arguments

1. key (string): The key that was unset.
2. oldValue (string): The value of key prior to being unset.

Transaction Manager Usage

Constructor

Arguments:

1. datastore (Datastore): The datastore to apply transactions to.

Example:

const store = new Datastore();
const manager = new TransactionManager(store);

Methods

begin()

Starts a new transaction.

Arguments:

None.

Returns:

Nothing.

Example:

manager.begin();

commit()

Starts a new transaction.

Arguments:

None.

Returns:

Nothing.

Example:

store.set('x', '10');
manager.begin();
store.set('x', '20');
manager.commit();
const result = store.get('x');
console.log(result);
// 20

rollback()

Starts a new transaction.

Arguments:

None.

Returns:

Nothing.

Example:

store.set('x', '10');
manager.begin();
store.set('x', '20');
manager.rollback();
const result = store.get('x');
console.log(result);
// 10

CLI Usage

Constructor

The Cli constructor will either use the datastore provided, or create its own. It will create its own TransactionManager instance.

Arguments:

1. datastore (Datastore): The datastore to attach the CLI to.

Example:

const store = new Datastore();
const cli = new Cli(store);

Methods

end()

Emits the end event.

Arguments:

None.

Returns:

Nothing.

Example:

cli.end();

Events

end

Emitted when a call to the end() method is made.

Prerequisites

You will need the following things properly installed on your computer.

• Git
• Node.js (with NPM)

Installation

• git clone <repository-url> this repository
• change into the new directory
• npm install
• npm run-script build
• npm start

Contributing

• Fork it!
• Create your feature branch: git checkout -b my-new-feature
• Commit your changes: git commit -am 'Add some feature'
• Push to the branch: git push origin my-new-feature
• Submit a pull request :D

License

MIT © Asa Rudick