label

The labeled statement can be used with break or continue statements. It is prefixing a statement with an identifier which you can refer to.

Syntax

label :
   statement

label

Any JavaScript identifier that is not a reserved word.

statement

Statements. break can be used with any labeled statement, and continue can be used with looping labeled statements.

Description

You can use a label to identify a loop, and then use the break or continue statements to indicate whether a program should interrupt the loop or continue its execution.

Note that JavaScript has NO goto statement, you can only use labels with break or continue.

In strict mode code, you can't use "let" as a label name. It will throw a SyntaxError (let is a reserved identifier).

Examples

Using a labeled continue with for loops

var i, j;

loop1:
for (i = 0; i < 3; i++) {      //The first for statement is labeled "loop1"
   loop2:
   for (j = 0; j < 3; j++) {   //The second for statement is labeled "loop2"
      if (i === 1 && j === 1) {
         continue loop1;
      }
      console.log('i = ' + i + ', j = ' + j);
   }
}

// Output is:
//   "i = 0, j = 0"
//   "i = 0, j = 1"
//   "i = 0, j = 2"
//   "i = 1, j = 0"
//   "i = 2, j = 0"
//   "i = 2, j = 1"
//   "i = 2, j = 2"
// Notice how it skips both "i = 1, j = 1" and "i = 1, j = 2"

Using a labeled continue statement

Given an array of items and an array of tests, this example counts the number of items that passes all the tests.

var itemsPassed = 0;
var i, j;

top:
for (i = 0; i < items.length; i++) {
  for (j = 0; j < tests.length; j++) {
    if (!tests[j].pass(items[i])) {
      continue top;
    }
  }

  itemsPassed++;
}

Using a labeled break with for loops

var i, j;

loop1:
for (i = 0; i < 3; i++) {      //The first for statement is labeled "loop1"
   loop2:
   for (j = 0; j < 3; j++) {   //The second for statement is labeled "loop2"
      if (i === 1 && j === 1) {
         break loop1;
      }
      console.log('i = ' + i + ', j = ' + j);
   }
}

// Output is:
//   "i = 0, j = 0"
//   "i = 0, j = 1"
//   "i = 0, j = 2"
//   "i = 1, j = 0"
// Notice the difference with the previous continue example

Using a labeled break statement

Given an array of items and an array of tests, this example determines whether all items pass all tests.

var allPass = true;
var i, j;

top:
for (i = 0; items.length; i++)
  for (j = 0; j < tests.length; i++)
    if (!tests[j].pass(items[i])) {
      allPass = false;
      break top;
    }

Using a labeled block with break

You can use labels within simple blocks, but only break statements can make use of non-loop labels.

foo: {
  console.log('face');
  break foo;
  console.log('this will not be executed');
}
console.log('swap');

// this will log:

// "face"
// "swap 

Labeled function declarations

Starting with ECMAScript 2015, labeled function declarations are now standardized for non-strict code in the web compatibility annex of the specification.

L: function F() {}

In strict mode code, however, this will throw a SyntaxError:

'use strict';
L: function F() {}
// SyntaxError: functions cannot be labelled

Generator functions can neither be labeled in strict code, nor in non-strict code:

L: function* F() {}
// SyntaxError: generator functions cannot be labelled

Specifications

Specification	Status	Comment
ECMAScript 3rd Edition (ECMA-262)	Standard	Initial definition. Implemented in JavaScript 1.2
ECMAScript 5.1 (ECMA-262) The definition of 'Labelled statement' in that specification.	Standard
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Labelled statement' in that specification.	Standard
ECMAScript 2017 Draft (ECMA-262) The definition of 'Labelled statement' in that specification.	Draft

Browser compatibility

See also

• break
• continue