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JavaScript object properties list

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A JavaScript object is a data structure that stores data as key-value pairs. Some commonly used properties of a JavaScript object include constructor, hasOwnProperty, prototype, toString, valueOf, isPrototypeOf, propertyIsEnumerable, and toLocaleString.

These properties can be used to manipulate and interact with JavaScript objects in a variety of ways.

PropertyDescription
constructorA reference to the constructor function that created the object.
hasOwnProperty(property)A method that returns a boolean indicating whether the object has a property with the specified name as a direct property of the object itself (as opposed to a property inherited from the object’s prototype chain).
prototypeA reference to the prototype object that the object is linked to. This is used to inherit properties and methods from the prototype.
toString()A method that returns a string representation of the object.
valueOf()A method that returns the primitive value of the object.
isPrototypeOf(object)A method that returns a boolean indicating whether the object is a prototype of the specified object.
propertyIsEnumerable(property)A method that returns a boolean indicating whether the specified property can be enumerated (i.e., whether it will show up in a for…in loop).
toLocaleString()A method that returns a localized string representation of the object.
toString()A method that returns a string representation of the object.
valueOf()A method that returns the primitive value of the object.

JavaScript object properties list example code

Simple example code of how you might use some of the properties of a JavaScript object:

// Create a simple object
const person = {
  firstName: "John",
  lastName: "Doe",
  age: 30,
  getFullName() {
    return `${this.firstName} ${this.lastName}`;
  }
};

// Use some of the object's properties
console.log(person.firstName); //"John"
console.log(person.age); //30
console.log(person.getFullName()); //"John Doe"
console.log(person.hasOwnProperty("age")); //true
console.log(person.hasOwnProperty("toString")); //false

Output:

JavaScript object properties list

How to list the properties of a JavaScript object?

Answer: To list the properties of a JavaScript object, you can use the Object.keys() method or the for...in loop.

Using Object.keys()

The Object.keys() method returns an array of a given object’s own property names in the same order as a for...in loop.

const person = {
  firstName: "John",
  lastName: "Doe",
  age: 30,
  email: "[email protected]"
};

const propertyNames = Object.keys(person);

console.log(propertyNames); // Output: ["firstName", "lastName", "age", "email"]

Using for...in loop

The for...in loop iterates over all the enumerable properties of an object, including its inherited properties from its prototype chain.

const person = {
  firstName: "John",
  lastName: "Doe",
  age: 30,
  email: "[email protected]"
};

for (let propertyName in person) {
  if (person.hasOwnProperty(propertyName)) {
    console.log(propertyName); // Output: firstName, lastName, age, email
  }
}

Comment if you have any doubts or suggestions on this JS Object topic.

Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.

OS: Windows 10

Code: HTML 5 Version

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