80 lines
1.9 KiB
Markdown
80 lines
1.9 KiB
Markdown
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---
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title: Labeled Statement
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---
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## Labeled Statement
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The **Labeled Statement** is used with the `break` and `continue` statements and serves to identify the statement to which the `break` and `continue` statements apply.
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### Syntax
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``` javascript
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labelname:
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statements
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```
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### Usage
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Without the use of a `labeled` statement the `break` statement can only break out of a loop or a `switch` statement. Using a `labeled` statement allows `break` to jump out of any code block.
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#### Example
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``` javascript
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foo: {
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console.log("This prints:");
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break foo;
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console.log("This will never print.");
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}
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console.log("Because execution jumps to here!")
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/* output
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This prints:
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Because execution jumps to here! */
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```
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When used with a `continue` statement the `labeled` statement allows you to skip a loop iteration, the advantage comes from being able to jump out from an inner loop to an outer one when you have nested loop statements. Without the use of a `labeled` statement you could only jump out of the existing loop iteration to the `next iteration of the same loop.`
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#### Example
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``` javascript
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// without labeled statement, when j==i inner loop jumps to next iteration
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function test() {
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for (var i = 0; i < 3; i++) {
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console.log("i=" + i);
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for (var j = 0; j < 3; j++) {
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if (j === i) {
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continue;
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}
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console.log("j=" + j);
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}
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}
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}
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/* output
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i=0 (note j=0 is missing)
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j=1
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j=2
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i=1
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j=0 (note j=1 is missing)
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j=2
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i=2
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j=0
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j=1 (note j=2 is missing)
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*/
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// using a labeled statement we can jump to the outer (i) loop instead
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function test() {
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outer: for (var i = 0; i < 3; i++) {
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console.log("i=" + i);
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for (var j = 0; j < 3; j++) {
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if (j === i) {
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continue outer;
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}
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console.log("j=" + j);
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}
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}
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}
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/*
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i=0 (j only logged when less than i)
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i=1
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j=0
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i=2
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j=0
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j=1
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*/
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```
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### More Information:
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<a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/label' target='_blank' rel='nofollow'>MDN</a>
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