JavaScript Label Statement

JavaScript is a versatile programming language that offers various features and statements to enhance code readability and control flow. One such statement is the label statement. In this article, we will explore what the label statement is, how it works, and provide examples to illustrate its usage.

What is the Label Statement?

The label statement is a JavaScript feature that allows you to associate a label with a block of code. This label can then be used with certain control flow statements to specify the flow of execution within your code.

Here is the syntax for the label statement:

:

The label name is an identifier followed by a colon (:). It can be any valid JavaScript identifier, such as a variable name.

Usage of the Label Statement

The label statement is primarily used in conjunction with the break and continue statements to control the flow of loops and switch statements.

Example 1: Using Label with the break Statement

Let’s start with an example that demonstrates the usage of the label statement with the break statement. Consider the following code:

outerLoop:
for (let i = 0; i < 5; i++) {
  for (let j = 0; j < 5; j++) {
    if (i === 2 && j === 2) {
      break outerLoop;
    }
    console.log(i, j);
  }
}

In this example, we have a nested loop. The outer loop is labeled as outerLoop using the label statement. Inside the nested loop, we have an if condition that checks if i is equal to 2 and j is equal to 2. If this condition is true, the break statement is executed, which terminates the outer loop labeled as outerLoop.

The output of this code will be:

0 0
0 1
0 2
0 3
0 4
1 0
1 1
1 2
1 3
1 4

As you can see, the loop terminates when i is 2 and j is 2, breaking out of both the inner and outer loops.

Example 2: Using Label with the continue Statement

Next, let’s explore an example that demonstrates the usage of the label statement with the continue statement. Consider the following code:

outerLoop:
for (let i = 0; i < 5; i++) {
  for (let j = 0; j < 5; j++) {
    if (i === 2 && j === 2) {
      continue outerLoop;
    }
    console.log(i, j);
  }
}

In this example, we have the same nested loop structure as before. However, instead of using the break statement, we use the continue statement with the label outerLoop. When the condition i === 2 and j === 2 is met, the continue statement is executed, which skips the current iteration of the outer loop and continues with the next iteration.

The output of this code will be:

0 0
0 1
0 2
0 3
0 4
1 0
1 1
1 2
1 3
1 4
2 0
2 1
2 3
2 4
3 0
3 1
3 2
3 3
3 4
4 0
4 1
4 2
4 3
4 4

As you can see, when i is 2 and j is 2, the iteration of the outer loop is skipped, but the inner loop continues normally.

Conclusion

The label statement in JavaScript provides a way to associate a label with a block of code, enabling you to control the flow of execution within loops and switch statements. By using labels with the break and continue statements, you can precisely control the behavior of your code. However, it is important to use labels sparingly and with caution, as excessive use of labels can make code harder to understand and maintain.

By understanding how to use the label statement effectively, you can enhance the readability and control flow of your JavaScript code.