@stdlib/utils-define-properties NPM

Define Properties

Define (and/or modify) object properties.

Installation

npm install @stdlib/utils-define-properties

Usage

var defineProperties = require( '@stdlib/utils-define-properties' );

defineProperties( obj, properties )

Defines (and/or modifies) object properties.

var objectKeys = require( '@stdlib/utils-keys' );

var obj = {};
defineProperties( obj, {
    'foo': {
        'value': 'bar',
        'writable': false,
        'configurable': false,
        'enumerable': true
    },
    'baz': {
        'value': 13,
        'enumerable': false
    }
});

// Retrieve all enumerable keys:
var keys = objectKeys( obj );
// returns [...]

The properties parameter is an object whose own enumerable property values are descriptors for the properties to be defined or modified. A property descriptor has the following optional properties:

configurable: boolean indicating if property descriptor can be changed and if the property can be deleted from the provided object. Default: false.
enumerable: boolean indicating if the property shows up when enumerating object properties. Default: false.
writable: boolean indicating if the value associated with the property can be changed with an assignment operator. Default: false.
value: property value.
get: function which serves as a getter for the property, or, if no getter, undefined. When the property is accessed, a getter function is called without arguments and with the this context set to the object through which the property is accessed (which may not be the object on which the property is defined due to inheritance). The return value will be used as the property value. Default: undefined.
set: function which serves as a setter for the property, or, if no setter, undefined. When assigning a property value, a setter function is called with one argument (the value being assigned to the property) and with the this context set to the object through which the property is assigned. Default: undefined.

Notes

Property descriptors come in two flavors: data descriptors and accessor descriptors. A data descriptor is a property that has a value, which may or may not be writable. An accessor descriptor is a property described by a getter-setter function pair. A descriptor must be one of these two flavors and cannot be both.

Examples

var defineProperties = require( '@stdlib/utils-define-properties' );

function Person( name ) {
    if ( !(this instanceof Person) ) {
        return new Person( name );
    }
    defineProperties( this, {
        'name': {
            'value': name,
            'writable': false
        },
        'greeting': {
            'get': function greet() {
                return 'Hello '+this.name;
            }
        }
    });
    return this;
}

var person = new Person( 'Simon' );

try {
    person.name = 'Peter';
} catch ( err ) {
    console.log( err.message );
}

var greeting = person.greeting;
// returns <string>

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.