JavaScript Object Literal
In JavaScript, an object literal is a simple way to define an object using a set of key-value pairs. You define an object literal by using curly braces {}
and specifying properties inside it.
const student ={
Name : "dheeraj",
Uid : 9856,
Dep : "cse",
Course : "BE",
Subj :['python','java','ai/ml']
};
Accessing Object Properties (Two Ways)
You can access the values of object properties in two ways:
Dot notation:
objectName.propertyName
console.log(student.name); // dheeraj console.log(student.uid); // 9856
Bracket notation:
objectName["propertyName"]
console.log(student["Name"]); // dheeraj console.log(student["Uid"]); // 9856
Automatic Conversion of Keys to Strings
JavaScript automatically converts keys to strings in an object. You can use null
, undefined
, numbers, or other types as keys, but they will all be converted to strings internally.
let obj = {
null: "This is null",
undefined: "This is undefined",
123: "This is a number"
};
console.log(obj["null"]); // Output: "This is null"
console.log(obj[undefined]); // Output: "This is undefined"
console.log(obj[123]); // output : This is a number
Adding, Updating, and Deleting Properties in Object Literal
Adding or Updating a Property: You can add or update properties using dot notation or bracket notation.
Deleting a property: You can delete a property using the
delete
operator.
const student ={
name : "dheeraj",
uid : 9856,
dep : "cse",
course : "BE",
subj :['python','java','ai/ml']
};
student.course="B tech";
student.gender="M";
Objects of Objects
Objects can contain other objects as properties, creating nested objects.
const classInfo = {
dheeraj: {
grade : "A+",
city : "pune"
},
david:{
grade : "f",
city : "london"
}
};
console.log(classInfo.dheeraj.city); // pune
Array of Objects
An array of objects is an array where each element is an object. This is useful for managing collections of related objects.
let employees = [
{ name: "Alice", age: 28 },
{ name: "Bob", age: 35 },
{ name: "Charlie", age: 32 }
];
console.log(employees[0].name); // Output: "Alice"
JavaScript Object vs Object Literal
JavaScript Object: It is a general term for any object in JavaScript. Objects can be created using the
Object()
constructor, or an object literal.Object Literal: It is a specific way to create an object using
{}
with key-value pairs directly written inside.Using
Object()
constructor:
let person = new Object();
person.name = "John";
person.age = 30;
- Using an object literal:
let person = {
name: "John",
age: 30
};
Key Difference*: The object literal is a simpler, more concise way to create objects compared to using the Object()
constructor.*
Math Object in JavaScript
The Math
object in JavaScript provides built-in methods for mathematical operations. You don't need to instantiate the Math
object, as it's a global object.
Common Math Methods:
Math.abs()
: Returns the absolute value of a number.Math.pow()
: Returns the base raised to the power of the exponent.Math.floor()
: Rounds a number down to the nearest integer.Math.ceil()
: Rounds a number up to the nearest integer.Math.random()
: Returns a random number between0
(inclusive) and1
(exclusive).
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PRACTICE QUESTION
Qs1. Create a program that generates a random number representing a dice roll.
[The number should be between 1 and 6].
let dice_roll = Math.random()*6;
Math.ceil(dice_roll);
Qs2. Create an object representing a car that stores the following properties for the car: name, model, color.
Print the car’s name.
const car={
name: "tata Harrier",
model: "top-782 M",
color: "Black"
};
console.log(car.name);
Qs3. Create an object Person with their name, age and city.
Edit their city’s original value to change it to “New York”.
Add a new property country and set it to the United States