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    defineProperties Redirect 1

    Summary

    The Object.defineProperties() method defines new or modifies existing properties directly on an object, returning the object.

    Syntax

    Object.defineProperties(obj, props)

    Parameters

    obj
    The object on which to define or modify properties.
    props
    An object whose own enumerable properties constitute descriptors for the properties to be defined or modified.

    Description

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

    Example

    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 = !!obj.enumerable;
        if (hasProperty(desc, "configurable"))
          d.configurable = !!obj.configurable;
        if (hasProperty(desc, "value"))
          d.value = obj.value;
        if (hasProperty(desc, "writable"))
          d.writable = !!desc.writable;
        if ( hasProperty(desc, "get") ) {
          var g = desc.get;
    
          if (!isCallable(g) && g !== "undefined")
            throw new TypeError("bad get");
          d.get = g;
        }
        if ( hasProperty(desc, "set") ) {
          var s = desc.set;
          if (!isCallable(s) && 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 Language Specification 5.1th Edition (ECMA-262) Standard Initial definition.
    Implemented in JavaScript 1.8.5
    ECMAScript Language Specification 6th Edition (ECMA-262) Draft  

    Browser compatibility

    Based on Kangax's compat tables.

    Feature Firefox (Gecko) Chrome Internet Explorer Opera Safari
    Basic support 4.0 (2) 5 (previous versions untested) 9 11.60 5
    Feature Firefox Mobile (Gecko) Android IE Mobile Opera Mobile Safari Mobile
    Basic support 4.0 (2) (Yes) ? 11.50 (Yes)

    See also

    Document Tags and Contributors

    Contributors to this page: Sheppy
    Last updated by: Sheppy,