Object.defineProperties()

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Die Object.defineProperties() Methode definiert neue, oder modifziert existierende Attribute direkt an einem Objekt und gibt das Objekt zurück.

Syntax

Object.defineProperties(obj, props)

Parameters

obj
The object on which to define or modify properties.
props
An object whose keys represent the names of properties to be defined or modified and whose values are objects describing those properties. Each value in props must be either a data descriptor or an accessor descriptor; it cannot be both (see Object.defineProperty() for more details).
Data descriptors and accessor descriptors may optionally contain 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.

A data descriptor also has the following optional keys:

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.

An accessor descriptor also has the following optional keys:

get
A function which serves as a getter for the property, or undefined if there is no getter. The function's return value will be used as the value of the 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 its only argument the new value being assigned to the property.
Defaults to undefined.

If a descriptor has neither of value, writable, get and set keys, it is treated as a data descriptor. If a descriptor has both value or writable and get or set keys, an exception is thrown.

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 Latest Draft (ECMA-262)
Die Definition von 'Object.defineProperties' in dieser Spezifikation.
Entwurf
ECMAScript 2015 (6th Edition, ECMA-262)
Die Definition von 'Object.defineProperties' in dieser Spezifikation.
Standard
ECMAScript 5.1 (ECMA-262)
Die Definition von 'Object.defineProperties' in dieser Spezifikation.
Standard Initial definition. Implemented in JavaScript 1.8.5

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid WebviewChrome für AndroidFirefox für AndroidOpera für AndroidSafari auf iOSSamsung InternetNode.js
definePropertiesChrome Vollständige Unterstützung 5Edge Vollständige Unterstützung 12Firefox Vollständige Unterstützung 4IE Vollständige Unterstützung 9Opera Vollständige Unterstützung 11.6Safari Vollständige Unterstützung 5WebView Android Vollständige Unterstützung JaChrome Android Vollständige Unterstützung 18Firefox Android Vollständige Unterstützung 4Opera Android Vollständige Unterstützung 12Safari iOS Vollständige Unterstützung JaSamsung Internet Android Vollständige Unterstützung Janodejs Vollständige Unterstützung Ja

Legende

Vollständige Unterstützung  
Vollständige Unterstützung

See also