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, andcontinue
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
.
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
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; }
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 3rd Edition | Standard | Initial definition. Implemented in JavaScript 1.2 |
ECMAScript 5.1 (ECMA-262) The definition of 'Labelled statement' in that specification. |
Standard | |
ECMAScript 6 (ECMA-262) The definition of 'Labelled statement' in that specification. |
Release Candidate |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |