break
The break
statement terminates the current loop or switch
statement and transfers program control to the statement following the terminated statement. It can also be used to jump past a labeled statement when used within that labeled statement.
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Syntax
js
break;
break label;
label
Optional-
Identifier associated with the label of the statement to break to. If the
break
statement is not nested within a loop orswitch
, then the label identifier is required.
Description
When break;
is encountered, the program breaks out of the innermost switch
or looping statement and continues executing the next statement after that.
When break label;
is encountered, the program breaks out of the statement labeled with label
and continues executing the next statement after that. The break
statement needs to be nested within the referenced label. The labeled statement can be any statement (commonly a block statement); it does not have to be another loop statement.
A break
statement, with or without a following label, cannot be used at the top level of a script, module, function's body, or static initialization block, even when the function or class is further contained within a loop.
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
.
js
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.
js
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. By using break outerBlock
, control is transferred to the end of the block statement marked as outerBlock
.
js
outerBlock: {
innerBlock: {
console.log("1");
break outerBlock; // breaks out of both innerBlock and outerBlock
console.log(":-("); // skipped
}
console.log("2"); // skipped
}
Unsyntactic break statements
A break
statement must be nested within any label it references. The following code also uses break
statements with labeled blocks, but generates a syntax error because its break
statement references block2
but it's not nested within block2
.
js
block1: {
console.log("1");
break block2; // SyntaxError: label not found
}
block2: {
console.log("2");
}
Syntax errors 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.
js
function testBreak(x) {
let i = 0;
while (i < 6) {
if (i === 3) {
(() => {
break;
})();
}
i += 1;
}
return i * x;
}
testBreak(1); // SyntaxError: Illegal break statement
js
block1: {
console.log("1");
(() => {
break block1; // SyntaxError: Undefined label 'block1'
})();
}
Specifications
Specification |
---|
ECMAScript Language Specification # sec-break-statement |
Browser compatibility
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