MemoryRecord

Description

A simple library that handles a few records easily.

Install

npm install js-memory-record

Simplest Example

class Gender extends MemoryRecord {
  static get define() {
    return [
      { key: "male"   },
      { key: "female" },
    ]
  }
}

gender = Gender.fetch("male")
gender.name          // => "male"
gender.code          // => 0

Gender.fetch(0).name // => "male"

More Example

Records Define

Return an array of Hash structures in define()

import MemoryRecord from 'js-memory-record'

export default class Fruit extends MemoryRecord {

  // Record definition.

  static get define() {
    return [
      { key: "apple",  name: "Poison Apple", price: 120, },
      { key: "melon",  name: "Green Melon",  price: 800, },
      { key: "peach",  name: "Pink Piece",   price: 200, },
    ]
  }

  // Define an instance method referencing an attribute.
  // Define it when accessing other than key, name and other attributes

  get full_name() {
    return `${this.name} (Now ${this.special_price} Gold)`
  }

  get special_price() {
    return Math.ceil(this.price / 2)
  }
}

fetch(key) - Key Access

Basic access by this method.

Fruit.fetch("apple").key        // => "apple"
Fruit.fetch("apple").name       // => "Poison Apple"
Fruit.fetch("apple").code       // => 0
Fruit.fetch("apple").index      // => 0

fetch(code) - Code Access

Code is something like database ID. Allocate in order from 0. Use it when you want to access by special index.

Fruit.fetch(0).name                     // => "Poison Apple"
Fruit.fetch(0) === Fruit.fetch("apple") // => true

Attributes can be referred to as properties

Fruit.fetch("apple").price      // => 120

Additional Defined Instance Methods

Define the Instance Metod freely and return the attributes in an easy-to-use form. This part is one of the merits of introducing this library.

Fruit.fetch("apple").special_price // => 60
Fruit.fetch("apple").full_name     // => "Poison Apple (Now 60 Gold)"

Unknown Key Access

There is no lookup() exception.

Fruit.lookup("grape")           // => null

In case of fetch() we will throw an exception.

Fruit.fetch("grape")            // (Throw Error)

The error message of the exception is displayed as follows.

Error: Fruit.fetch("grape") does not match anything
keys: ["apple","melon","peach"]
codes: [0,1,2]

The cause of the error is displayed in an easy-to-understand manner.

Array Access

Fruit.values                    // => [{...}, {...}, {...}]

Fruit.values.map(e => e.key)    // => ["apple", "melon", "peach"]

Other Class Methods

Fruit.keys      // => ["apple", "melon", "peach"]
Fruit.codes     // => [0, 1, 2]
Fruit.names     // => ["Poison Apple", "Green Melon", "Pink Piece"],

We do not use this class methods much. But it may be useful for debugging.

code can be explicitly specified

static get define() {
  return [
    { code: 1, key: "apple", },
    { code: 2, key: "melon", },
    { code: 4, key: "peach", },
  ]
}

Fruit.codes    // => [1, 2, 4]

This is like managing database ID yourself. We do not recommend it. It is only useful if you need consistency with old data.

How to reset the array of records later

Replace the entire record internally held. I do not recommend this method much. But it may be useful in emergency.

Fruit.memory_record_reset([
  { key: "foo" },
  { key: "bar" },
])

Fruit.fetch("foo").key    // => "foo"

Build Setup

# install dependencies
npm install

# build for production with minification
npm run build

# run unit tests
npm test

memory_record_reset

akicho8/js-memory-record