JavaScript if-else

JavaScript conditional statements allow programs to make decisions based on specific conditions. They control the flow of execution, enabling different actions for different scenarios.

JavaScript if-statement

It is a conditional statement that determines whether a specific action or block of code will run based on a condition. If the condition is true, the code executes; if false, it does not.

Syntax

if (condition) {
    // Code to be executed if the condition is true
}

Now let's understand this with the help of an example:

// JavaScript program to illustrate If statement
let age = 19;

if (age > 18)
console.log("Congratulations, You are eligible to drive");

Congratulations, You are eligible to drive

JavaScript if-else statement

The if-else statement allows you to execute one block of code if the condition is true and another block if the condition is false. It's a way to handle two possible outcomes based on a condition.

Syntax

if (condition)
{
    // Executes this block if
    // condition is true
}
else
{
    // Executes this block if
    // condition is false
}

Now let's understand this with the help of example

// JavaScript program to illustrate If-else statement
let i = 10;

if (i < 15)
    console.log("i is less than 15");
else
    console.log("I am Not in if");

i is less than 15

JavaScript nested-if statement

JavaScript lets you put an if statement inside another if statement. This is called a nested if, where one if or else is inside another.

Syntax

if (condition1) 
{
   // Executes when condition1 is true
   if (condition2) 
   {
      // Executes when condition2 is true
   }
}

Now let's understand this with the help of example

// JavaScript program to illustrate nested-if statement
let i = 10;

if (i == 10) {  // First if statement
    if (i < 15) {
        console.log("i is smaller than 15");
        // Nested - if statement
        // Will only be executed if statement above
        // it is true
        if (i < 12)
            console.log("i is smaller than 12 too");
        else
            console.log("i is greater than 15");
    }
}

i is smaller than 15
i is smaller than 12 too

JavaScript if-else-if statement

The if-else-if ladder is used to check multiple conditions in sequence. Once a true condition is found, its block executes, and the rest are skipped.

Syntax

if (condition)
    statement;
else if (condition)
    statement;
.
.
else
    statement;

Now let's understand this with the help of example

// JavaScript program to illustrate nested-if statement
let i = 20;
if (i == 10)
    console.log("i is 10");
else if (i == 15)
    console.log("i is 15");
else if (i == 20)
    console.log("i is 20");
else
    console.log("i is not present");

i is 20