Who should take this course?

Grokking JavaScript Fundamentals

Rate this course

Ask Author

Contribute

Back to course home

0% completed

Vote For New Content

Introduction

Who should take this course?

Course Overview

Introduction to JavaScript

JavaScript Basics

JavaScript - Hello World

JavaScript - Comments

Quiz

JavaScript Variables and Operators

JavaScript - Variables

JavaScript - Operators

Quiz

JavaScript Conditionals

Introduction to Conditional Statements in JavaScript

JavaScript - If...Else

JavaScript - Switch Case

Quiz

JavaScript Objects

Introduction to Objects in JavaScript

JavaScript - Number

JavaScript - Boolean

JavaScript - Math

JavaScript - Date

Quiz

JavaScript - Functions

Introductions to Function in JavaScript

JavaScript - Variable Scope

JavaScript - Default Parameters

JavaScript - Arrow Functions

Quiz

JavaScript - String and Arrays

Introduction to Strings in JavaScript

JavaScript - String Methods

Introduction to Array in JavaScript

JavaScript - Array Methods

Quiz

JavaScript Loops

Introduction to loops in JavaScript

JavaScript - for loop

JavaScript - while loop

JavaScript - do-while loop

JavaScript - for-in loop

JavaScript - for-of loop

JavaScript - Loop Control

Quiz

JavaScript - Maps and Sets

JavaScript - Maps

JavaScript - Sets

Quiz

Conclusion

Where to Go from Here

JavaScript - If...Else

The if statement

In JavaScript, the if statement is a fundamental control structure that enables you to execute different blocks of code based on whether a condition is true or false. This flexibility is essential for creating dynamic and interactive web applications.

Syntax

The syntax for an if statement is simple:

if (condition) {
    // block of code to be executed if the condition is true
}

condition: An expression evaluated in Boolean context. If the condition evaluates to true, the code within the block is executed.

Example

Write a program to check if a user is old enough to vote.

Javascript

. . . .

In this example, if the age variable is 18 or more, the message "You are old enough to vote!" is logged to the console.

The else statement

The else statement complements an if statement by specifying a block of code to be executed when the if condition evaluates to false. It acts as the default or fallback action when none of the if or else if conditions are met.

The execution flow of if...else statement is as given in the diagram below.

Syntax

Follow the syntax below to use the else statement with if statement:

Javascript

. . . .

Example

Extending the voting example, let's provide feedback if the user is not old enough to vote:

Javascript

// Declare a variable 'age' and initialize it with the value 16
var age = 16;
// Check if 'age' is greater than or equal to 18
if (age >= 18) {
    // This block of code is executed if the condition is true (age is 18 or older)
    console.log("You are old enough to vote!");
} else {
    // This block of code is executed if the condition is false (age is less than 18)
    console.log("Sorry, you are not old enough to vote.");
}

. . . .

Here, if age is less than 18, the message "Sorry, you are not old enough to vote." is displayed.

The else if statement

The else if statement is an extension of the if...else structure, allowing for multiple conditions to be checked in sequence. It's especially useful when you have several possible outcomes and need to test them one by one until a true condition is found.

Syntax

The else if statement allows you to test multiple conditions sequentially:

Javascript

. . . .

Example

Let's say you're creating a grading system where grades are assigned based on the score:

Javascript

// Declare a variable 'score' and initialize it with the value 75
var score = 75;
// Check if 'score' is greater than or equal to 90
if (score >= 90) {
    // This block is executed if 'score' is 90 or higher
    console.log("Grade A");
} else if (score >= 80) {
    // This block is executed if 'score' is 80 or higher but less than 90
    console.log("Grade B");
} else if (score >= 70) {
    // This block is executed if 'score' is 70 or higher but less than 80
    console.log("Grade C");
} else {
    // This block is executed if none of the above conditions are true (score is less than 70)
    console.log("Grade F");
}

. . . .

In this example, a score of 75 results in "Grade C". The program checks each condition in order until one is true, then executes the corresponding code block.

For practice modify the value of score to 85 or 95 and see what is printed on the console.

The if...else statement in JavaScript is a powerful tool for adding decision-making to your programs. By understanding how to use if, else, and else if statements together, you can control the flow of your code based on conditions, making your web applications more dynamic and responsive to user input.

Introduction to Conditional Statements in JavaScript

JavaScript - Switch Case

Mark as Completed

On this page

The if statement

Syntax

Example

The else statement

Syntax

Example

The else if statement

Syntax

Example