break Keyword

break Keyword

The break statement terminates the current loop, switch, or label statement and transfers program control to the statement following the terminated statement.

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Syntax

break;
break label;

Description

The break statement includes an optional label that allows the program to break out of a labeled statement. The break statement needs to be nested within the referenced label. The labeled statement can be any block statement; it does not have to be preceded by a loop statement.

A break statement, with or without a following label, cannot be used within the body of a function that is itself nested within the current loop, switch, or label statement that the break statement is intended to break out of.

Examples

break in while loop

The following function has a break statement that terminates the while loop when i is 3, and then returns the value 3 * x.

function testBreak(x) {
  let i = 0;

  while (i < 6) {
    if (i === 3) {
      break;
    }
    i += 1;
  }

  return i * x;
}

break in switch statements

The following code has a break statement that terminates the switch statement when a case is matched and the corresponding code has run.

const food = "sushi";

switch (food) {
  case "sushi":
    console.log("Sushi is originally from Japan.");
    break;
  case "pizza":
    console.log("Pizza is originally from Italy.");
    break;
  default:
    console.log("I have never heard of that dish.");
    break;
}

break in labeled blocks

The following code uses break statements with labeled blocks. A break statement must be nested within any label it references. Notice that innerBlock is nested within outerBlock.

outerBlock: {
  innerBlock: {
    console.log('1');
    break outerBlock; // breaks out of both inner_block and outer_block
    console.log(':-('); // skipped
  }
  console.log('2'); // skipped
}

break in labeled blocks that throw

The following code also uses break statements with labeled blocks, but generates a SyntaxError because its break statement is within block1 but references block2. A break statement must always be nested within any label it references.

block1: {
  console.log('1');
  break block2; // SyntaxError: label not found
}

block2: {
  console.log('2');
}

break within functions

SyntaxErrors are also generated in the following code examples which use break statements within functions that are nested within a loop, or labeled block that the break statements are intended to break out of.

function testBreak(x) {
  let i = 0;

  while (i < 6) {
    if (i === 3) {
      (function () {
        break;
      })();
    }
    i += 1;
  }

  return i * x;
}

testBreak(1); // SyntaxError: Illegal break statement

block_1: {
  console.log('1');
  (function () {
    break block_1; // SyntaxError: Undefined label 'block_1'
  })();
}