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define-accessor2

1.0.1 • Public • Published

define-accessor2

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⭐️ Define feature-rich properties using decorators or plain functions. An extended version of Object.defineProperty ⭐️

Features

  • no dependencies
  • supports decorators for methods and class properties
  • supports legacy and current draft of decorator specification
  • lazy properties
  • cached properties - cache the value returned by the accessor getter. Cached value can be flushed later
  • validation hook
  • Joi validation out of the box
  • built-in basic type system (see Built-in types)
  • automatically flushes getter cache after changing related properties
  • defining custom validators
  • isolated contexts to define validators in a local scope
  • chaining methods - can create chaining methods like getPropName and setPropName
  • type predicates (isNumber, isNull etc)

Installation

Install for node.js using npm/yarn:

$ npm install define-property2 --save
$ yarn add define-property2
const {defineAccessor}= require('define-accessor2');

Playground

  1. Clone https://github.com/DigitalBrainJS/define-accessor2.git repo
  2. Run npm install to install dev-dependencies
  3. Open sandbox/sandbox.js file with a basic example of using library decorators
  4. Run this file using npm run sandbox or npm run sandbox:watch command to see the result

Usage examples

A basic example of using library decorators (with plugin-proposal-decorators and plugin-proposal-class-properties babel plugins):

const {type, string, number, array} = require("define-accessor2");
 
class Cat {
    @string
    name = '';
    @type(string | number)
    foo = 123;
    @array
    bar = [];
}
 
const cat = new Cat();
cat.name = 'Lucky'; // Ok
cat.foo = 123;
cat.foo = '123';
cat.bar = [1, 2, 3];
 
cat.name = 123; // TypeError: Property name accepts String, but number given
cat.foo = true; // TypeError: Property foo accepts String|Number, but boolean given
cat.bar= {}; //Property bar accepts Array, but object given

More complex:

const {type, cached, touches, validate, accessor, defineValidator, string}= require('define-accessor2');
const hash = require('object-hash');
const validator= require('validator');
const Joi= require('@hapi/joi');
 
//import all methods as validators predicates
defineValidator(validator);
 
class Model{
    // cached value
    @cached
    get sha(){
        console.log('calc sha');
        return hash(this);
    }
    // this prop affects 'sha' prop
    @touches('sha')
    @string
    name= 'anonymous';
 
    @touches('sha')
    @type('number|string')
    foo= 30;
    // configure all the necessary accessor features in one decorator (recommended way)
    @accessor({
        touches: 'sha',
        validate: 'isEmail'
    })
    email= '';
    // Joi validator can be used out of the box for complex properties validation
    @validate(Joi.array().items(Joi.string()))
    labels= [];
}
 
const model= new Model();
 
console.log(model.name); // 'anonymous'
console.log(model.sha); // calc sha
console.log(model.sha); // just return the cached value
model.name= 'admin';
console.log(model.sha); // calc sha
model.email= 'admin@google.com';
console.log(model.sha);
model.foo= true;
model.labels= ['123'];

Just using plain functions without any decorators

     const {defineAccessor, TYPE_NUMBER, TYPE_STRING}= require('define-accessor2');
     const obj= {};
 
     defineAccessor(obj, 'someProp', {
         type: 'string|number'
     });
     //or using type bit mask
     defineAccessor(obj, 'someProp', {
         type: TYPE_STRING|TYPE_NUMBER
     });

Validate with Joi:

     const {defineAccessor}= require('define-accessor2');
     const Joi = require('@hapi/joi');
     const user= {};
 
     defineAccessor(user, 'age', {
        validate: Joi.number().integer().min(0).max(100),
        set(newValue, prevValue){
            //do some work
            return newValue; //set newValue to the property age
        }
     });
 
    user.age= 30; //ok, now age= 30
    user.age= 150; //ValidationError: value (150) is not valid for property (age). Reason: "value" must be less than or equal to 100

Custom validator:

     //import library and create a new context for a local validator definition
     const {defineAccessor, defineValidator}= require('define-accessor2').newContext();
     const validator= require('validator');
     const model= {};
 
    defineValidator({
        mongoId: validator.isMongoId
    });
 
    defineAccessor(model, 'id', {
        validate: 'mongoId'
    });
const {defineAccessor, flushAccessor}= require('define-accessor2');
const hash = require('object-hash');
 
const obj= {};
 
const normalize = (str)=> str.replace(/^\w/, (str)=> str.toUpperCase());
 
const {_name}= defineAccessor(obj, {
    hash: {
        get(){
            return hash(this);
        },
        cached: true
    },
    name: {
        validate(value, {reject, set}){
            typeof value!=='string' && reject('must be a string');
            value= value.trim();
            !/^[a-zA-Z]+$/.test(value) && reject('only a-zA-Z allowed');
            // alternative way to reject
            if( value.length<= 3) return 'length should be greater than 3';
            // returning other values than 'true' and 'undefined' treated, as rejection,
            // strings are considered as rejection reason
            set(value); // change the value
        },
        set: normalize,
        touches: ['hash'],
        value: 'Jon'
    },
 
    email: {
        validate: validator.isEmail
    }
 
}, {prefix: '_'})
 

Functional diagram

Accessor functional diagram

API

define-accessor2

module.exports ⏏

The default library context. Call context.newContext() to return a new context inherited from the current. This allows you to create an isolated library scope, which does not affect any others in case of defining a custom validator.

Kind: Exported member

module.exports.defineAccessor(obj, prop, [descriptor]) ⇒ PrivatePropKey

Defines a single accessor

Kind: instance method of module.exports

Param Type Description
obj Object target object
prop PropertyKey property key
[descriptor] AccessorDescriptor

Example

defineAccessor(obj, "age", {
    get(){
        return 99;
    }
})
     

module.exports.defineAccessor(obj, props, [descriptor]) ⇒ Array.<PrivatePropKey>

Defines several accessors with the same descriptor

Kind: instance method of module.exports

Param Type Description
obj Object target object
props Array.<PropertyKey> properties list
[descriptor] AccessorDescriptor

Example

defineAccessor(obj, ["name", "surname"], {
    get(privateValue, propKey){
        switch(propKey){
            case 'name':
             return 'John';
            case 'surname':
             return 'Connor';
        }
    }
})
     

module.exports.defineAccessor(obj, props, [options]) ⇒ Object.<PrivatePropKey>

Defines several accessors using hash map

Kind: instance method of module.exports
Returns: Object.<PrivatePropKey> - object of private properties that refer to the defined accessors

Param Type Description
obj Object target object
props Object.<PropertyKey> properties hash map
[options] Object
[options.prefix] String add prefix for each property key of the returned object

Example

const {_name, _surname}= defineAccessor(obj, {
    name: {
        get(){
            return 'John';
        }
    },
 
    surname: {
        get(){
            return 'Connor';
        }
    }
}, {
    prefix: '_'
})

module.exports.flushAccessor(obj, ...props) ⇒ boolean

flush accessor's cache

Kind: instance method of module.exports
Returns: boolean - true if flushed successfully

Param Type Description
obj Object target object
...props PropertyKey public accessor's key

Example

defineAccessor(obj, "hash", {
    get(){
        return calcObjectSHA(this);
    }
})
flushAccessor(obj, 'hash')

module.exports.privateSymbol(obj, prop) ⇒ Symbol | null

retrieve the private accessor symbol assigned to the accessor

Kind: instance method of module.exports

Param Type
obj Object
prop PropertyKey

module.exports.defineValidator(name, fn) ⇒ this

Defines a new validator in the current library context

Kind: instance method of module.exports

Param Type Description
name String validator's name
fn ValidatorPredicate validator predicate function

Example

const validator = require('validator');
defineValidator('email', validator.isEmail);
     

module.exports.defineValidator(validators)

Defines a new validator in the current library context

Kind: instance method of module.exports

Param Type
validators Object

Example

const validator = require('validator');
defineValidator({
 email: validator.isEmail,
 ip: validator.isIP
});

module.exports.newContext() ⇒ Context

creates a new library context

Kind: instance method of module.exports
Example

const {defineAccessor, flushAccessor, defineValidator}= require('define-accessor2').newContext()
//define custom validators for the current and inherited from the current contexts only
defineValidator({
    even: (value)=> typeof value && value % 2===0,
    odd: (value)=> typeof value && Math.abs(value % 2)===1,
});

module.exports.accessor(accessorDescriptor) ⇒ MethodDecorator

accessor decorator

Kind: instance method of module.exports

Param
accessorDescriptor

module.exports.accessor([get], [set], [accessorDescriptor]) ⇒ MethodDecorator

Kind: instance method of module.exports

Param Type Description
[get] function getter function, can be omitted
[set] function setter function, can be omitted
[accessorDescriptor] AccessorDescriptor accessor descriptor

module.exports.lazy() ⇒ MethodDecorator

lazy decorator

Kind: instance method of module.exports

module.exports.cached() ⇒ MethodDecorator

cached decorator

Kind: instance method of module.exports

module.exports.chains() ⇒ MethodDecorator

cached decorator

Kind: instance method of module.exports

module.exports.type(type) ⇒ MethodDecorator

type decorator

Kind: instance method of module.exports

Param Type
type BasicType

module.exports.validate(validator) ⇒ MethodDecorator

validate decorator

Kind: instance method of module.exports

Param Type
validator BasicType

module.exports.touches(props) ⇒ MethodDecorator

touches decorator

Kind: instance method of module.exports

Param Type
props PropertyKey | Array.<PropertyKey>

module.exports.undefined() ⇒ MethodDecorator

Undefined decorator

Kind: instance method of module.exports

module.exports.null() ⇒ MethodDecorator

Null decorator

Kind: instance method of module.exports

module.exports.boolean() ⇒ MethodDecorator

Boolean decorator

Kind: instance method of module.exports

module.exports.number() ⇒ MethodDecorator

Number decorator

Kind: instance method of module.exports

module.exports.string() ⇒ MethodDecorator

string decorator

Kind: instance method of module.exports

module.exports.function() ⇒ MethodDecorator

Function decorator

Kind: instance method of module.exports

module.exports.object() ⇒ MethodDecorator

Object decorator

Kind: instance method of module.exports

module.exports.symbol() ⇒ MethodDecorator

Symbol decorator

Kind: instance method of module.exports

module.exports.bigint() ⇒ MethodDecorator

BigInt decorator

Kind: instance method of module.exports

module.exports.integer() ⇒ MethodDecorator

Integer decorator

Kind: instance method of module.exports

module.exports.infinity() ⇒ MethodDecorator

Infinity decorator

Kind: instance method of module.exports

module.exports.nan() ⇒ MethodDecorator

NaN decorator

Kind: instance method of module.exports

module.exports.date() ⇒ MethodDecorator

Date decorator

Kind: instance method of module.exports

module.exports.promise() ⇒ MethodDecorator

Promise decorator

Kind: instance method of module.exports

module.exports.regexp() ⇒ MethodDecorator

RegExp decorator

Kind: instance method of module.exports

module.exports.error() ⇒ MethodDecorator

Error decorator

Kind: instance method of module.exports

module.exports.set() ⇒ MethodDecorator

Set decorator

Kind: instance method of module.exports

module.exports.map() ⇒ MethodDecorator

Map decorator

Kind: instance method of module.exports

module.exports~Context

Library context class

Kind: inner class of module.exports

module.exports~SetterFunction ⇒ any

Kind: inner typedef of module.exports
Returns: any - value to store in the private property

Param Type Description
newValue any new value to set
currentValue any current private value
propKey PropertyKey public property key
privateKey PrivatePropKey private property key

module.exports~GetterFunction ⇒ any

Kind: inner typedef of module.exports

Param Type Description
currentValue any current private value
propKey PropertyKey public property key

module.exports~ValidateFunction ⇒ Boolean

Kind: inner typedef of module.exports
Throws:

  • Error
Param Type Description
value any value to validate
propKey PropertyKey public property key

module.exports~PropertyKey : String | Symbol

Kind: inner typedef of module.exports

module.exports~PrivatePropKey : Symbol

Kind: inner typedef of module.exports

module.exports~AccessorDescriptor : Object

Accessor's descriptor.

Kind: inner typedef of module.exports
Properties

Name Type Default Description
[get] GetterFunction getter function
[set] SetterFunction setter function
[writable] Boolean false if setter is not present indicates whether accessor's value can be set
[enumerable] Boolean false
[configurable] Boolean false
[cached] Boolean false cache getter result until it will be flushed by flushAccessor or other related accessor
[lazy] Boolean false indicates whether the accessor should be a lazy computing property
[virtual] Boolean false if true a private property is not created
[chains] Boolean false create get/set chains for property (like getPropName()/setPropName(value))
[touches] PropertyKey | Array.<PropertyKey> a key of accessor whose value depends on this
[type] BasicType built-type
[validate] ValidateFunction validator function
[value] * value to set after initialization

module.exports~ValidatorPredicate ⇒ Boolean

Kind: inner typedef of module.exports

Param Type Description
value any value to test

module.exports~BasicType : Number | String

Basic type.

Kind: inner typedef of module.exports

module.exports~AssertionFunction ⇒ Boolean

Kind: inner typedef of module.exports
Returns: Boolean - false if test failed

Param Type Description
value Any value to test

Built-in types

The library's type system consist of native JS types and extended pseudotypes. The following types do not overlap, unlike native javascript types. For example, null is not an object, NaN is not a number, and so on.

  • Undefined (TYPE_UNDEFINED)
  • Null (TYPE_NULL)
  • Boolean (TYPE_BOOLEAN)
  • Number (TYPE_NUMBER)
  • String (TYPE_STRING)
  • Function (TYPE_FUNCTION)
  • Object (TYPE_OBJECT)
  • Symbol (TYPE_SYMBOL)
  • BigInt (TYPE_BIGINT)
  • Array (TYPE_ARRAY)
  • Infinity (TYPE_INFINITY)
  • NaN (TYPE_NAN)
  • Date (TYPE_DATE)
  • Promise (TYPE_PROMISE)
  • RegExp (TYPE_REGEXP)
  • Error (TYPE_ERROR)
  • Set (TYPE_SET)
  • Map (TYPE_MAP)

An exception is the integer pseudotype which is an integer and a number types.

  • Integer (TYPE_INTEGER)

Special type:

  • Any (TYPE_ANY)

There are predicates for each type named like isUndefined(value), isNumber(value) etc.

You can combine these types:

  • type: 'string|number' // strings
  • type: TYPE_STRING|TYPE_NUMBER //bit mask
  • type: string|number // decorators are implicitly converted to a type bit mask using the valueOf() internal method

Decorators

The library supports both versions of the decorators specification (legacy & current draft). There are following decorators:

  • lazy
  • cached
  • touches
  • type
  • validate
  • accessor
  • and decorators for each basic type (string, number, array etc. see Built-in types) Each decorator has valueOf method that returns a type bit mask, so it's possible to pass decorators as a type: @type(number|string)

Contribution

Feel free to fork, open issues, enhance or create pull requests.

License

The MIT License Copyright (c) 2019 Dmitriy Mozgovoy robotshara@gmail.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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