Object

Overview

The Object type is used to store various keyed collections and more complex entities. Nearly all objects in JavaScript are instances of Object.

For more information see: Object (MDN).

Methods Summarized

Methods Detailed

assign(target, sources)

Copy the values of all enumerable own properties from one or more source objects to a target object.

Parameters

• Object target The target object.

• Array sources The source object(s).

Returns: Object The target object.

Sample

var object1 = { a: 1, b: 2, c: 3};
var object2 = Object.assign({c: 4, d: 5}, object1);
application.output(object2.c, object2.d);

create(object)

Creates a new object, using an existing object to provide the newly created object's prototype.

Parameters

• Object object The object which should be the prototype of the newly-created object.

Returns: Object A new object with the specified prototype object.

Sample

const person = {
	isHuman: false,
	printIntroduction: function () {
		application.output("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"

create(object, properties)

Creates a new object, using an existing object to provide the newly created object's prototype and properties.

Parameters

• Object object The object which should be the prototype of the newly-created object.

• Object properties ;

Returns: Object A new object with the specified prototype object.

Sample

var o = Object.create({}, { p: { value: 42 } });
application.output(o.p);

defineProperties(object, properties)

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

Parameters

• Object object The object on which to define or modify properties.

• Object properties An object whose own enumerable properties constitute descriptors for the properties to be defined or modified. 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.

Returns: Object The object that was passed to the function.

Sample

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

defineProperty(object, property, descriptor)

Allows a precise addition to or modification of a property on an object.

Parameters

• Object object The object on which to define or modify properties.

• Object property The name of the property to be defined or modified.

• Object descriptor The descriptor for the property being defined or modified.

Returns: Object The object that was passed to the function.

Sample

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

entries(object1)

Returns an array whose elements are arrays corresponding to the enumerable string-keyed property key-value pairs found directly upon object.

Parameters

• Object object1 An object.

Returns: Array An array of the given object's own enumerable string-keyed property key-value pairs. Each key-value pair is an array with two elements: the first element is the property key (which is always a string), and the second element is the property value.

Sample

const object1 = { a: 'somestring',  b: 42,  c: false};
application.output(Object.entries(object1));

freeze(object)

Freezes an object: that is, prevents new properties from being added to it; prevents existing properties from being removed; and prevents existing properties, or their enumerability, configurability, or writability, from being changed. In essence the object is made effectively immutable.

Parameters

• Object object The object to freeze.

Returns: Object The object that was passed to the function.

Sample

const object1 = { property1: 42 };
const object2 = Object.freeze(object1);
object2.property1 = 33;
application.output(object2.property1); //expected result is 42

fromEntries(entries)

Transforms a list of key-value pairs into an object

Parameters

• Array entries A list of objects. Each object is an array with two values, first value is the key second one is the value.

Returns: Object A new object whose properties are given by the entries of the array.

Sample

application.output(Object.fromEntries(entries));

getOwnPropertyDescriptor(object, property)

Permits examination of the precise description of a property.

Parameters

• Object object The object in which to look for the property.

• Object property The name of the property whose description is to be retrieved.

Returns: Object A property descriptor of the given property if it exists on the object, undefined otherwise.

Sample

const object1 = { property1: 42 };
const descriptor1 = Object.getOwnPropertyDescriptor(object1, 'property1');
application.output(descriptor1.configurable); // expected output: true
application.output(descriptor1.value); //expected result is 42

getOwnPropertyNames(object)

Returns an array of all properties (including non-enumerable properties) found directly upon a given object.

Parameters

• Object object The object whose enumerable and non-enumerable own properties are to be returned.

Returns: Array An array of strings that correspond to the properties found directly upon the given object.

Sample