JavaScript break

Summary: in this tutorial, you’ll learn how to use the JavaScript break statement to terminate a loop prematurely.

The label statement #

In JavaScript, you can label a statement for later use. Here’s the syntax of the label statement:

label: statement;Copy

In this syntax, the label can be any valid identifier. For example, the following shows how to label a for loop using the outer label:

outer: for (let i = 0; i < 5; i++) {
    console.log(i);
}Copy

Once you define a label, you can reference it in the break or continue statement.

Introduction to JavaScript break statement #

The break statement prematurely terminates a loop such as for, do...while, and while loop, a switch, or a label statement. Here’s the syntax of the break statement:

break [label];Copy

In this syntax, the label is optional if you use the break statement in a loop or switch. However, if you use the break statement with a label statement, you need to specify it.

This tutorial focuses on how to use the break statement to terminate the loop prematurely.

Using JavaScript break statement in a for loop #

The following for loop statement outputs five numbers from 0 to 4:

for (let i = 0; i < 5; i++) {
  console.log(i);
}Copy

Output:

0
1
2
3
4Copy

To terminate the for loop prematurely, you can use a break statement. For example, the following illustrates how to use a break statement inside a for loop:

for (let i = 0; i < 5; i++) {
  console.log(i);
  if (i == 2) {
    break;
  }
}Copy

Output:

0
1
2Copy

In this example, we use an if statement inside the loop. If the current value of i is 2, the if statement executes the break statement that terminates the loop.

This flowchart illustrates how the break statement works in a for loop:

Using the break statement to terminate a nested loop #

A nested loop has one loop inside another. For example, the following uses a nested for loop to output a pair of numbers from 1 to 3:

for (let i = 1; i <= 3; i++) {
  for (let j = 1; j <= 3; j++) {
    console.log(i, j);
  }
}Copy

Output:

1 1
1 2
1 3
2 1
2 2
2 3
3 1
3 2
3 3Copy

If you use a break statement inside an inner loop, it only terminates the enclosing loop. For example:

for (let i = 1; i <= 3; i++) {
  for (let j = 1; j <= 3; j++) {
    if (i + j == 4) {
      break;
    }
    console.log(i, j);
  }
}Copy

Output:

1 1
1 2
2 1Copy

In this example, if the sum of i and j is 4, the break statement terminates the inner loop. To terminate the nested loop, you use a label statement. For example:

outer: for (let i = 1; i <= 3; i++) {
  for (let j = 1; j <= 3; j++) {
    if (i + j == 4) {
      break outer;
    }
    console.log(i, j);
  }
}Copy

Output:

1 1
1 2Copy

In this example, we label the outer loop with the label outer. Inside the inner loop, we specify the outer label in the break statement. The break statement to terminate the nested loop if the sum of i and j is 4.

Using JavaScript break statement in a while loop #

The following output five numbers from 1 to 5 to the console using a while loop:

let i = 0;

while (i < 5) {
  i++;
  console.log(i);
}Copy

Output:

1
2
3
4
5Copy

Like a for loop, the break statement terminates a while loop prematurely. For example:

let i = 0;

while (i < 5) {
  i++;
  console.log(i);
  if (i == 3) {
    break;
  }
}Copy

Output:

1
2
3Copy

In this example, when the current value of i is 3, the break statement terminates the loop. Therefore, you see only three numbers in the output.

The following flowchart illustrates how the break statement works in a while loop:

Using JavaScript break statement in a do…while loop #

The following example uses a do...while statement to output five numbers from 0 to 5 to the console:

let i = 0;

do {
  i++;
  console.log(i);
} while (i < 5);Copy

Output:

1
2
3
4
5Copy

Like a while loop, you can use a break statement to terminate a do...while loop. For example:

let i = 0;

do {
  i++;
  console.log(i);
  if (i == 3) {
    break;
  }
} while (i < 5);Copy

Output:

1
2
3Copy

The following flowchart shows how the break statement works in a do while loop:

Summary #

• Use the break statement to terminate a loop including for, while, and do...while prematurely.
• The break statement terminates the enclosing loop in a nested loop. To terminate the nested loop, you use a label statement.

Quiz #