Object

Object

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Methods

(static) assign(target, …sources) → {object}

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Copies all enumerable own properties from one or more source objects to a target object. MDN

Example
var object1 = { a: 1, b: 2, c: 3 };

Object.assign(object1, { c: 4, d: 5 });
// Returns: Object { a: 1, b: 2, c: 4, d: 5 }
Parameters:
Name Type Attributes Description
target object

The target object — what to apply the sources’ properties to, which is returned after it is modified.
sources Object <repeatable>

The source object(s) — objects containing the properties you want to apply.
Returns:
  • The target object.
Type
object

(static) create(proto, propertiesopt) → {object}

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Creates a new object, using an existing object as the prototype of the newly created object. MDN

Example
var person = {
  isHuman: false,
  printIntroduction: function () {
    console.log('My name is ' + this.name + '. Am I human? ' + this.isHuman);
  }
};

var me = Object.create(person);

me.name = 'Matthew'; // "name" is a property set on "me", but not on "person"
me.isHuman = true; // inherited properties can be overwritten
me.printIntroduction();
// expected output: "My name is Matthew. Am I human? true"
Parameters:
Name Type Attributes Description
proto object

The object which should be the prototype of the newly-created object.
properties object <optional>
Returns:
  • A new object with the specified prototype object and properties.
Type
object

(static) defineProperties(obj, props) → {object}

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Defines new or modifies existing properties directly on an object, returning the object. MDN

Example
var object1 = {};

Object.defineProperties(object1, {
  property1: { value: 42, writable: true },
  property2: {}
});

console.log(object1.property1); // Outputs: 42
Parameters:
Name Type Description
obj object

The object on which to define or modify properties.
props object

An object whose keys represent the names of properties to be defined or modified and whose values are objects describing those properties.
Returns:
  • The object that was passed to the function.
Type
object

(static) defineProperty(obj, prop, descriptor) → {object}

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Defines a new property directly on an object, or modifies an existing property on an object, and returns the object. MDN

Example
var object1 = {};

Object.defineProperty(object1, 'property1', {
  value: 42,
  writable: false
});

object1.property1 = 77; // throws an error in strict mode
console.log(object1.property1); // Outputs: 42
Parameters:
Name Type Description
obj object

The object on which to define the property.
prop string

The name or Symbol of the property to be defined or modified.
descriptor object

The descriptor for the property being defined or modified.
Returns:
  • The object that was passed to the function.
Type
object

(static) freeze(obj) → {object}

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Freezes an object. A frozen object can no longer be changed. MDN

Example
var obj = { prop: 42 };

Object.freeze(obj);

obj.prop = 33; // Throws an error in strict mode
console.log(obj.prop); // Outputs: 42
Parameters:
Name Type Description
obj object

The object to freeze.
Returns:
  • The object that was passed to the function.
Type
object

(static) getOwnPropertyDescriptor(obj, prop) → {*}

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From ECMAScript 5.1 ECMA-262 MDN

Example
var object1 = { property1: 42 };
var descriptor1 = Object.getOwnPropertyDescriptor(object1, 'property1');

console.dir(descriptor1.configurable); // Outputs: true
console.log(descriptor1.value); // Outputs: 42
Parameters:
Name Type Description
obj object

The object in which to look for the property.
prop string

The name or Symbol of the property whose description is to be retrieved.
Returns:
  • A property descriptor of the given property if it exists on the object, undefined otherwise.
Type
*

(static) getOwnPropertyNames(obj) → {Array.<string>}

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Returns an array of all properties (including non-enumerable properties except for those which use Symbol) found directly in a given object. MDN

Example
var object1 = { a: 1, b: 2, c: 3 };
console.dir(Object.getOwnPropertyNames(object1));
// expected output: Array ["a", "b", "c"]
Parameters:
Name Type Description
obj object

The object whose enumerable and non-enumerable properties are to be returned.
Returns:
  • An array of strings that corresponds to the properties found directly in the given object.
Type
Array.<string>

(static) getPrototypeOf(obj) → {true|null}

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From ECMA-262 5.1 edition MDN

Example
var prototype1 = {};
var object1 = Object.create(prototype1);

console.dir(Object.getPrototypeOf(object1) === prototype1); // Outputs: true
Parameters:
Name Type Description
obj object

The object whose prototype is to be returned.
Returns:
  • The prototype of the given object. If there are no inherited properties, null is returned.
Type
true | null

(static) is(value1, value2) → {boolean}

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Determines whether two values are the same value. MDN

Example
Object.is('foo', 'foo'); // true
Object.is('foo', 'bar'); // false
Object.is([], []);       // false
var foo = { a: 1 };
var bar = { a: 1 };
Object.is(foo, foo);     // true
Object.is(foo, bar);     // false
Parameters:
Name Type Description
value1 *

The first value to compare.
value2 *

The second value to compare.
Returns:
  • A Boolean indicating whether or not the two arguments are the same value.
Type
boolean

(static) keys(object) → {Array.<string>}

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Returns an array of a given object's own enumerable property names, in the same order as we get with a normal loop. MDN

Example
var object1 = { a: 'somestring', b: 42, c: false };

Object.keys(object1);
// Returns: Array ['a', 'b', 'c']
Parameters:
Name Type Description
object object
Returns:
  • An array of strings
Type
Array.<string>

(static) values(obj) → {Array}

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Returns an array of a given object's own enumerable property values, in the same order as that provided by a for...in loop (the difference being that a for-in loop enumerates properties in the prototype chain as well). MDN

Example
const object1 = { a: 'somestring', b: 42, c: false };

Object.values(object1);
// Returns: Array ['somestring', 42, false]
Parameters:
Name Type Description
obj object

The object whose enumerable own property values are to be returned.
Returns:
  • An array containing the given object's own enumerable property values.
Type
Array