JavaScript break Statement

In this chapter, we will learn about the JavaScript break statement. The break statement is used to terminate the execution of a loop, switch, or labeled statement prematurely. We will cover:

• What is the break Statement?
• Syntax
• Using the break Statement in Loops
• Using the break Statement in switch Statements
• Breaking Out of Nested Loops
• Simple Programs using the break Statement

What is the break Statement?

The break statement is used to exit a loop or switch statement before it has completed all its iterations or cases. It immediately transfers the control to the statement following the loop or switch.

Syntax

break; 

Using the break Statement in Loops

Example

// Initialize the counter variable let i = 0; // Loop until the condition is false while (i < 10) { // Check if the counter is equal to 5 if (i === 5) { // Exit the loop when the counter is 5 break; } // Print the current value of the counter console.log(i); // Increment the counter i++; } 

Output:

0 1 2 3 4 

In the example above, the break statement exits the loop when the counter i reaches 5.

Using the break Statement in switch Statements

Example

// Define the day of the week let day = 2; // Determine the name of the day switch (day) { case 1: // Case for Sunday console.log("Sunday"); // Exit the switch statement break; case 2: // Case for Monday console.log("Monday"); // Exit the switch statement break; case 3: // Case for Tuesday console.log("Tuesday"); // Exit the switch statement break; default: // Default case for other days console.log("Another day"); } 

Output:

Monday 

In the example above, the break statement exits the switch statement after the matching case is executed.

Breaking Out of Nested Loops

Example

// Outer loop for (let i = 0; i < 3; i++) { // Inner loop for (let j = 0; j < 3; j++) { // Check if the inner counter is 1 if (j === 1) { // Exit the inner loop break; } // Print the values of the counters console.log(`i = ${i}, j = ${j}`); } } 

Output:

i = 0, j = 0 i = 1, j = 0 i = 2, j = 0 

In the example above, the break statement exits only the inner loop when j is 1, and the outer loop continues to execute.

Simple Programs using the break Statement

Program 1: Find the First Even Number in an Array

// Define an array of numbers let numbers = [1, 3, 5, 8, 10]; // Loop through the array for (let i = 0; i < numbers.length; i++) { // Check if the current number is even if (numbers[i] % 2 === 0) { // Print the first even number console.log("First even number:", numbers[i]); // Exit the loop break; } } 

Output:

First even number: 8 

Program 2: Search for a Character in a String

// Define the string to search let str = "hello world"; // Define the character to find let charToFind = 'o'; // Loop through the string for (let i = 0; i < str.length; i++) { // Check if the current character matches the character to find if (str[i] === charToFind) { // Print the index of the character console.log("Character found at index:", i); // Exit the loop break; } } 

Output:

Character found at index: 4 

Program 3: Check for Prime Number

// Define the number to check let number = 17; // Initialize a flag to indicate if the number is prime let isPrime = true; // Loop from 2 to the square root of the number for (let i = 2; i <= Math.sqrt(number); i++) { // Check if the number is divisible by the current value of i if (number % i === 0) { // Set the flag to false if the number is not prime isPrime = false; // Exit the loop break; } } // Check if the number is prime if (isPrime) { console.log(number + " is a prime number."); } else { console.log(number + " is not a prime number."); } 

Output:

17 is a prime number. 

Conclusion

In this chapter, you learned about the JavaScript break statement, including its syntax and how to use it in loops and switch statements. We also covered breaking out of nested loops and provided various use cases with simple programs to demonstrate the usage of the break statement. The break statement is used for controlling the flow of your code and exiting loops or switch statements prematurely. In the next chapter, we will explore the JavaScript continue statement and how to use it to skip iterations in loops.