label

Summary

Provides a statement with an identifier that you can refer to using a break or continue statement.

For example, 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.

Version Information

Statement
Implemented in JavaScript 1.2
ECMA Version ECMA-262, Edition 3

Syntax

label :
   statement

Parameters

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.

Avoid using labels

Labels are not very commonly used in JavaScript since they make programs harder to read and understand. As much as possible, avoid using labels and, depending on the cases, prefer calling functions or throwing an error.

Examples

continue Example

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;
      } else {
         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"

Example 2 (continue)

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++;
}

Example 3 (break)

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;
    }

See also

Document Tags and Contributors

Last updated by: Havvy,