JavaScript If-else Statement

In JavaScript, the if-else statement is used to control the flow of the program based on conditions.

If Statement

Syntax:

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

Example:

let x = 10;

if (x > 5) {
  console.log("x is greater than 5");
}

If-else Statement

Syntax:

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

Example:

let hour = 14;

if (hour < 12) {
  console.log("Good morning!");
} else {
  console.log("Good afternoon!");
}

If-else if-else Statement

Syntax:

if (condition1) {
  // Code to be executed if condition1 is true
} else if (condition2) {
  // Code to be executed if condition2 is true
} else {
  // Code to be executed if none of the conditions are true
}

Example:

let grade = 85;

if (grade >= 90) {
  console.log("A");
} else if (grade >= 80) {
  console.log("B");
} else {
  console.log("C");
}

Nested If-else Statements

Syntax:

if (condition1) {
  // Code to be executed if condition1 is true
  if (condition2) {
    // Code to be executed if both condition1 and condition2 are true
  } else {
    // Code to be executed if condition1 is true and condition2 is false
  }
} else {
  // Code to be executed if condition1 is false
}

Example:

let num = 15;

if (num > 0) {
  if (num % 2 === 0) {
    console.log("Positive even number");
  } else {
    console.log("Positive odd number");
  }
} else if (num < 0) {
  console.log("Negative number");
} else {
  console.log("Zero");
}

 

Summary

The if-else statement allows you to execute different blocks of code based on whether a specified condition is true or false. It provides a way to create decision-making logic in your JavaScript programs.