Grokking JavaScript Fundamentals
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JavaScript - Loop Control
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In JavaScript, controlling the flow of loops is crucial for managing how and when loops start, execute, and terminate. This control is achieved through various statements, including label, continue, and break statements. Each serves a unique purpose in enhancing the flexibility and efficiency of loop operations.

Label Statement

A label provides a statement with an identifier that allows you to refer to it elsewhere in your code, particularly with break and continue statements. Labels are useful for breaking out of nested loops or continuing a loop iteration at a specific point in nested loops.

Syntax

Javascript
Javascript
. . . .

Parameters

  • labelName: Any valid JavaScript identifier.
  • statement: Any statement to label.

Example

In this example, we use a label with a break statement to exit from a nested loop.

Javascript
Javascript
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This code iterates over a pair of nested loops, but when both i and j equal 1, it breaks out of the outer loop entirely, thanks to the outerLoop label.

Continue Statement

The continue statement skips the current iteration of a loop and continues with the next iteration. It's particularly useful when a specific condition within the loop doesn't require the execution of the remaining loop body.

Syntax

Javascript
Javascript
. . . .
  • Optionally, you can specify a label to continue the next iteration of the labeled loop.

Example

Here's how you can use continue to skip certain iterations in a loop.

Javascript
Javascript
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This loop prints the numbers 0 to 4, except for 2, because the continue statement skips the loop's remaining body when i is 2.

Break Statement

The break statement terminates the loop immediately when executed. It's used to exit from a loop before it has iterated over all its elements, usually when a certain condition is met.

Syntax

Javascript
Javascript
. . . .
  • Just like with continue, a label can be specified to break out of a specific loop in nested loops.

Beginner Friendly Example

This example demonstrates using break to exit a loop early.

Javascript
Javascript
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The loop will print the numbers 0 to 2. When i equals 3, the break statement is executed, terminating the loop before all iterations are complete.

Through the use of label, continue, and break statements, JavaScript provides powerful tools for controlling loop execution. These control statements enhance the language's flexibility, allowing for more precise and efficient looping constructs.

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