JavaScript – Page 16

JavaScript Object Methods

Object methods are actions that can be performed on objects.

A method is a function definition stored as a property value.

Property	Value
firstName	John
lastName	Doe
age	50
eyeColor	blue
fullName	function() {return this.firstName + ” ” + this.lastName;}

Example

const person = {
  firstName: "John",
  lastName: "Doe",
  id: 5566,
  fullName: function() {
    return this.firstName + " " + this.lastName;
  }
};

In the example above, this refers to the person object :

this.firstName means the firstName property of person. Continue reading JavaScript Object Methods

JavaScript Object Properties

An Object is an Unordered Collection of Properties

Properties are the most important part of JavaScript objects.

Properties can be changed, added, deleted, and some are read only.

Accessing JavaScript Properties

The syntax for accessing the property of an object is:

// objectName.property
let age = person.age;

or

//objectName["property"]
let age = person["age"];

or

//objectName[expression]
let age = person[x];

Examples

person.firstname + " is " + person.age + " years old.";
person["firstname"] + " is " + person["age"] + " years old.";
let x = "firstname";
let y = "age";
person[x] + " is " + person[y] + " years old.";

Continue reading JavaScript Object Properties

JavaScript Objects

Object Properties

A real life car has properties like weight and color:

car.name = Fiat, car.model = 500, car.weight = 850kg, car.color = white.

Car objects have the same properties, but the values differ from car to car.

Object Methods

A real life car has methods like start and stop:

car.start(), car.drive(), car.brake(), car.stop().

Car objects have the same methods, but the methods are performed at different times. Continue reading JavaScript Objects

JavaScript Functions

A JavaScript function is a block of code designed to perform a particular task.

A JavaScript function is executed when “something” invokes it (calls it).

Example

// Function to compute the product of p1 and p2
function myFunction(p1, p2) {
  return p1 * p2;
}

JavaScript Function Syntax

A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses ().

Function names can contain letters, digits, underscores, and dollar signs (same rules as variables). Continue reading JavaScript Functions

JavaScript Data Types

JavaScript has 8 Datatypes

String
Number
Bigint
Boolean
Undefined
Null
Symbol
Object

The Object Datatype

The object data type can contain both built-in objects, and user defined objects:

Built-in object types can be:

objects, arrays, dates, maps, sets, intarrays, floatarrays, promises, and more.

Examples

// Numbers:
let length = 16;
let weight = 7.5;

// Strings:
let color = "Yellow";
let lastName = "Johnson";

// Booleans
let x = true;
let y = false;

// Object:
const person = {firstName:"John", lastName:"Doe"};

// Array object:
const cars = ["Saab", "Volvo", "BMW"];

// Date object:
const date = new Date("2022-03-25");

Continue reading JavaScript Data Types

JavaScript Assignment

JavaScript Assignment Operators

Assignment operators assign values to JavaScript variables.

Operator	Example	Same As
=	x = y	x = y
+=	x += y	x = x + y
-=	x -= y	x = x – y
*=	x *= y	x = x * y
/=	x /= y	x = x / y
%=	x %= y	x = x % y
**=	x **= y	x = x ** y

Continue reading JavaScript Assignment

JavaScript Arithmetic

JavaScript Arithmetic Operators

Arithmetic operators perform arithmetic on numbers (literals or variables).

Operator	Description
+	Addition
–	Subtraction
*	Multiplication
**	Exponentiation (ES2016)
/	Division
%	Modulus (Remainder)
++	Increment
—	Decrement

Continue reading JavaScript Arithmetic

JavaScript Operators

Javascript operators are used to perform different types of mathematical and logical computations.

Examples:

The Assignment Operator = assigns values

The Addition Operator + adds values

The Multiplication Operator * multiplies values

The Comparison Operator > compares values

JavaScript Assignment

The Assignment Operator (=) assigns a value to a variable:

Assignment Examples

let x = 10;

Continue reading JavaScript Operators

JavaScript Const

The const keyword was introduced in ES6 (2015)

Variables defined with const cannot be Redeclared

Variables defined with const cannot be Reassigned

Variables defined with const have Block Scope

Cannot be Reassigned

A variable defined with the const keyword cannot be reassigned:

Example

const PI = 3.141592653589793;
PI = 3.14;      // This will give an error
PI = PI + 10;   // This will also give an error

Continue reading JavaScript Const

JavaScript Let

The let keyword was introduced in ES6 (2015)

Variables declared with let have Block Scope

Variables declared with let must be Declared before use

Variables declared with let cannot be Redeclared in the same scope

Block Scope

Before ES6 (2015), JavaScript did not have Block Scope.

JavaScript had Global Scope and Function Scope.

ES6 introduced the two new JavaScript keywords: let and const. Continue reading JavaScript Let