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O método  Object.defineProperties() define uma nova propriedade ou modifica uma existente no objeto, retornando o objeto.

Syntax

Object.defineProperties(obj, propriedades)

Parâmetros

obj
O objeto no qual se cria ou modifica suas propriedades.
propriedades
An object whose own enumerable properties constitute descriptors for the properties to be defined or modified. Property descriptors present in objects come in two main flavors: data descriptors and accessor descriptors (see Object.defineProperty() for more details). Descriptors have the following keys:
configurable
true if and only if the type of this property descriptor may be changed and if the property may be deleted from the corresponding object.
Defaults to false.
enumerable
true if and only if this property shows up during enumeration of the properties on the corresponding object.
Defaults to false.
value
The value associated with the property. Can be any valid JavaScript value (number, object, function, etc).
Defaults to undefined.
writable
true if and only if the value associated with the property may be changed with an assignment operator.
Defaults to false.
get
A function which serves as a getter for the property, or undefined if there is no getter. The function return will be used as the value of property.
Defaults to undefined.
set
A function which serves as a setter for the property, or undefined if there is no setter. The function will receive as only argument the new value being assigned to the property.
Defaults to undefined.

Return value

The object that was passed to the function.

Description

Object.defineProperties, in essence, defines all properties corresponding to the enumerable own properties of props on the object obj object.

Example

var obj = {};
Object.defineProperties(obj, {
  'property1': {
    value: true,
    writable: true
  },
  'property2': {
    value: 'Hello',
    writable: false
  }
  // etc. etc.
});

Polyfill

Assuming a pristine execution environment with all names and properties referring to their initial values, Object.defineProperties is almost completely equivalent (note the comment in isCallable) to the following reimplementation in JavaScript:

function defineProperties(obj, properties) {
  function convertToDescriptor(desc) {
    function hasProperty(obj, prop) {
      return Object.prototype.hasOwnProperty.call(obj, prop);
    }

    function isCallable(v) {
      // NB: modify as necessary if other values than functions are callable.
      return typeof v === 'function';
    }

    if (typeof desc !== 'object' || desc === null)
      throw new TypeError('bad desc');

    var d = {};

    if (hasProperty(desc, 'enumerable'))
      d.enumerable = !!desc.enumerable;
    if (hasProperty(desc, 'configurable'))
      d.configurable = !!desc.configurable;
    if (hasProperty(desc, 'value'))
      d.value = desc.value;
    if (hasProperty(desc, 'writable'))
      d.writable = !!desc.writable;
    if (hasProperty(desc, 'get')) {
      var g = desc.get;

      if (!isCallable(g) && typeof g !== 'undefined')
        throw new TypeError('bad get');
      d.get = g;
    }
    if (hasProperty(desc, 'set')) {
      var s = desc.set;
      if (!isCallable(s) && typeof s !== 'undefined')
        throw new TypeError('bad set');
      d.set = s;
    }

    if (('get' in d || 'set' in d) && ('value' in d || 'writable' in d))
      throw new TypeError('identity-confused descriptor');

    return d;
  }

  if (typeof obj !== 'object' || obj === null)
    throw new TypeError('bad obj');

  properties = Object(properties);

  var keys = Object.keys(properties);
  var descs = [];

  for (var i = 0; i < keys.length; i++)
    descs.push([keys[i], convertToDescriptor(properties[keys[i]])]);

  for (var i = 0; i < descs.length; i++)
    Object.defineProperty(obj, descs[i][0], descs[i][1]);

  return obj;
}

Specifications

Specification Status Comment
ECMAScript 5.1 (ECMA-262)
The definition of 'Object.defineProperties' in that specification.
Padrão Initial definition. Implemented in JavaScript 1.8.5
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Object.defineProperties' in that specification.
Padrão  
ECMAScript Latest Draft (ECMA-262)
The definition of 'Object.defineProperties' in that specification.
Padrão em tempo real  

Browser compatibility

Feature Firefox (Gecko) Chrome Edge Internet Explorer Opera Safari
Basic support 4.0 (2) 5 (Yes) 9 11.60 5
Feature Firefox Mobile (Gecko) Android Edge IE Mobile Opera Mobile Safari Mobile
Basic support 4.0 (2) (Yes) (Yes) ? 11.5 (Yes)

See also

Etiquetas do documento e colaboradores

 Colaboradores desta página: LucianoDos
 Última atualização por: LucianoDos,