defeasy v0.0.3

defeasy

defeasy is a small library. it helps you define data and accessor properties.

install

npm install defeasy

usage

var defeasy = require('defeasy');

defeasy(UserDefinedClass.prototype);

or

var defeasy = require('defeasy')(); // defined at Object.prototype

now, you can call defeasy function for initialization. defeasy function has basic usage:

defeasy( [target=Object.prototype [, aliases={} [, writable=false [, enumerable=true ,configurable=false]]]] );

defeasy function defines methods listed at methods section to target and it has some properties that you can use them as option parameter at defeasy methods.

• target: define defeasy methods at this prototype or instance
• aliases: rename defeasy functions(ex: {'readOnly':'read_only'})
• writable: writable value for defeasy methods descriptor
• enumerable: enumerable value for defeasy methods descriptor
• configurable: configurable value for defeasy methods descriptor

defeasy methods

instance.defeasy(prop, value , value1, option=defeasy.NONE)

• prop: name of property. must be string.
• value: for data-property, it must be javascript data: number, string, date, function etc. if you want to define a accessor-property ( getter, setter functions for a key ), you must call this method with two parameters such as they are functions.
• option: attributes of property. it must be a property returned by defeasy initialization function. you can use attributes with | operator (bitwise or). defeasy.WRITABLE: define property as writable defeasy.ENUMERABLE: define property as enumerable defeasy.CONFIGURABLE: define property as configurable defeasy.READONLY: define as enumerable, not writable and not configurable * defeasy.READ_WRITE: define as writable and configurable. (= defeasy.WRITABLE | defeasy.CONFIGURABLE)_ defeasy.DEFAULT (defeasy.ALL, defeasy.DEFAULT_ASSIGN): defined as like by assigning, all attributes are true defeasy.NONE (defeasy.DEFAULT_DEFINE): all attributes are false. defeasy.USE_PROTO: define property at prototype of instance. defeasy.OTHERS_UNDEFINED: it just for accessor-property. if property is already defined and you want to define a new setter(getter) function for it, you can write over getter(setter) as undefined with this option.

var defeasy = require('defeasy')(UserDefined.prototype);
var userdf = new UserDefined();

// data-property
userdf.defeasy('prop', 'string-value', defeasy.READ_ONLY);
console.log(userdf.prop); // string-value
desc = Object.getOwnPropertyDescriptor(userdf, 'prop');
desc.writable === false && desc.configurable === false && desc.enumerable === true // true

// accessor-property
getter = function(){ return this.x; };
setter = function(newval){ this.x = newval * 2 };
userdf.defeasy('accessor', getter, setter, defeasy.DEFAULT);

instance.readOnly(prop, value , option=defeasy.ENUMERABLE)

defines property as not writable and not configurable.

instance.readWrite(prop, value ,option=defeasy.READ_WRITE)

defines property as writable and configurable

instance.accessor(prop, getter, setter , option=defeasy.NONE)

defines a accessor-property. getter and setter parameters must be function. if you want to define a new getter/setter for already defined accessor-property, you can set as undefined it's setter/getter via passing undefined argument and using defeasy.OTHERS_UNDEFINED

instance.accessor('accprop', function(){return this.v;}, undefined, defeasy.CONFIGURABLE|defeasy.OTHERS_UNDEFINED);
desc = Object.getOwnPropertyDescriptor(instance, 'accprop');
desc.set === undefined // true

instance.getter(prop, getter , option=defeasy.ENUMERABLE|defeasy.CONFIGURABLE)

alias for instance.accessor(prop, getter, undefined, option)

instance.setter(prop, setter , option=defeasy.ENUMERABLE|defeasy.CONFIGURABLE)

alias for instance.accessor(prop, undefined, setter, option)

instance.nonExtensibleMe(), instance.sealMe(), instance.freezeMe()

they are alias functions for Object.preventExtensions(instance), Object.seal(instance), Object.freeze(instance)

define a property at prototype of instance

instance.readWrite('shared', 'shared content', defeasy.ALL|defeasy.USE_PROTO);

var new_instance = new UserDefined();

console.log(new_instance.shared);