geheugen

A memoisation toolkit.

Installation

npm install --save @kjots/geheugen

Usage

As an ES6 module

import 'promise.prototype.finally';

import { memoise } from '@kjots/geheugen';

let memo = memoise({ factory: () => getAsyncValue() });

let promise = memo.resolve()
    .then(asyncValue => { ... })
    
memo.reset();

As an ES5 module

require('babel-polyfill');
require('promise.prototype.finally');

var memoise = require('@kjots/geheugen').memoise;

var memo = memoise({ factory: function () { return getAsyncValue(); } });

var promise = memo.resolve()
    .then(function (asyncValue) { ... })
    
memo.reset();

In a browser

<script src="babel-polyfill/dist/polyfill.js"></script>
<script src="promise.prototype.finally/finally.js"></script>

<script src="@kjots/geheugen/dist/geheugen.js"></script>

<script>
    var memo = geheugen.memoise({ factory: function () { return getAsyncValue(); } });

    var promise = memo.resolve()
        .then(function (asyncValue) { ... })
    
    memo.reset();
</script>

API

Memo

constructors

new Memo({ Q, singleton, dependencies, onSet, onReset factory, promise, value })

Q

Type: Class

Default: Promise

The promise implementation.

The promise implementation should at a minimum implement the following methods:

• Promise.resolve()
• Promise.all()

Note: The promise implementation must implement the .finally() promise method. A polyfill for the ES6 Promise API can be found at https://www.npmjs.com/package/promise.prototype.finally.

singleton

Type: Boolean

Default: true

The singleton flag.

dependencies

Type: Array<Memo>

Default: []

The dependencies.

onSet

Type: Function

Default: (value) => {}

The set event handler.

The set event handler will be invoked when the set() method is invoked.

onReset

Type: Function

Default: () => {}

The reset event handler.

The reset event handler will be invoked when the reset() method is invoked.

factory

Type: Function

Default: () => {}

The factory.

promise

Type: Promise

The promise.

value

The value.

methods

resolve()

Resolve the memo.

If the memo has a value and the singleton flag is set

Return a promise resolved with the value.

If the memo has a promise

Return the promise.

Otherwise

Invoke the factory and return a promise for the returned value.

The factory will be invoked via .then() of a promise resolved with the values of all of the dependencies.

Whilst the promise is pending it will be stored on the memo. When the promise is fulfilled the stored promise will be removed.

The returned value will be stored on the memo.

get()

Return the value the the memo.

set()

Update the value of the memo.

The set event handler will be invoked before the value is updated. If the set event handler throws an error the set operation will be aborted.

Any memo that has specified this memo as a dependency will be reset.

reset()

Remove the value from the memo.

The reset event handler will be invoked before the value is removed. If the reset event handler throws an error the reset operation will be aborted.

Any memo that has specified this memo as a dependency will also be reset.

resetDependants()

Reset all memos that have specified this memo as a dependency.

properties

Q

Type: Class

The promise implementation.

singleton

Type: Boolean

The singleton flag.

dependencies

Type: Array<Memo>

The dependencies.

onSet

Type: Function

The set event handler.

onReset

Type: Function

The reset event handler.

factory

Type: Function

The factory.

promise

Type: Promise

The promise.

value

The value.

dependants

Type: Array<Memo>

The dependants.

Any memo that has specified this memo as a dependency will be added to this array.