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Concept visual
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// Adding or changing an object property Object.defineProperty(object, property, descriptor) // Adding or changing object properties Object.defineProperties(object, descriptors) // Accessing a Property Object.getOwnPropertyDescriptor(object, property) // Accessing Properties Object.getOwnPropertyDescriptors(object) // Returns all properties as an array Object.getOwnPropertyNames(object) // Accessing the prototype Object.getPrototypeOf(object) JavaScript Object.defineProperty()
Object.defineProperty() method can be used to:
Object.defineProperty( object, property, descriptor )
This example adds a new property to an object:
// Create an Object:
const person = {
firstName: "John", lastName :
"Doe", language : "EN"
};// Add a Property Object.defineProperty(person, "year",
{value:"2008"});This example changes a property value:
// Create an Object:
const person = {
firstName: "John", lastName : "Doe", language : "EN"
};// Change a Property Object.defineProperty(person, "language",
{value : "NO"});All properties have a name. In addition they also have a value. The value is one of the property's attributes. Other attributes are: enumerable, configurable, and writable. These attributes define how the property can be accessed (is it readable?, is it writable?) In JavaScript, all attributes can be read, but only the value attribute can be changed (and only if the property is writable). ( ECMAScript 5 has methods for both getting and setting all property attributes)
The following property meta data can be changed: writable : true // Property value can be changed enumerable : true // Property can be enumerated configurable : true // Property can be reconfigured writable : false // Property value can not be changed enumerable : false // Property can be not enumerated configurable : false // Property can be not reconfigured Getters and setters can also be changed: // Defining a getter get: function() { return language }
Formula
// Defining a setter set: function(value) { language = value }Object.defineProperty(person, "language", {writable:false}); This example makes language not enumerable: Object.defineProperty(person, "language", {enumerable:false});
Object.getOwnPropertyNames() method can:
Object.getOwnPropertyNames( object )
This example gets all properties of an object:
// Create an Object const person = {
firstName: "John", lastName : "Doe", language : "EN"
};// Get all Properties
Object.getOwnPropertyNames(person);
Object.getOwnPropertyNames()will also list properties that is not enumerable:
// Create an Object const person = {
firstName: "John", lastName : "Doe", language : "EN"
};// Set the language Property not enumerable Object.defineProperty(person, "language", {enumerable:false}); // Get all Properties
Object.getOwnPropertyNames(person);
JavaScript Object.keys()Object.keys() method can:
Object.keys( object )