JavaScript Label Statement

In JavaScript, the label statement is used to label a block of code. A labeled statement can be used with loops and control flow statements to provide a target for the break and continue statements.

Syntax:

Label:
    statement (loop or block of code)

Keywords to be used:

• Label: A unique string that is Used to define the name of the block or loop.
• Statement: It can be a loop or block.
• Break: Used to terminate the loop or block of code.
• Continue: Used to terminate or jump from the current iteration of the loop.

Label statement with for loops: In this section, the user will learn to assign a unique label to multiple loops. Also, we will use the break and continue keywords with the multiple loops. The below examples will demonstrate the use of labels using loops.

Examples of JavaScript Label Statement

Example 1: Using the break keyword with labeled loops. Users can terminate the outer loop from the inner loop using the label.

Javascript

let sum = 0, a = 1;

// Label for outer loop
outerloop: while (true) {
    a = 1;

    // Label for inner loop
    innerloop: while (a < 3) {
        sum += a;
        if (sum > 12) {

            // Break outer loop from inner loop
            break outerloop;
        }
        console.log("sum = " + sum);
        a++;
    }
}

Output

sum = 1
sum = 3
sum = 4
sum = 6
sum = 7
sum = 9
sum = 10
sum = 12

Example 2: Using the continue keyword with labeled loops. Users can jump to the outer loop from the inner loop using the label. When the ‘ a=2 and sum < 12’ condition executes true, it doesn’t print the sum as we are terminating that iteration of the inner loop using the ‘continue’ keyword. When condition inside if statement executes true, it will jump to the outer loop.

Javascript

let sum = 0, a = 1;

// Label for outerloop
outerloop: while (sum < 12) {
    a = 1;

      // Label for inner loop
      innerloop: while (a < 3) {
        sum += a;
        if (a === 2 && sum < 12) {
              // Jump to outer loop from inner loop
              continue outerloop;
        }
        console.log("sum = " + sum + " a = " + a);
        a++;
      }
}

Output

sum = 1 a = 1
sum = 4 a = 1
sum = 7 a = 1
sum = 10 a = 1
sum = 12 a = 2

Example 3: Using the label statement with a block of code. Users can terminate the execution of a labeled block using the break keyword. You can observe that code after the break keyword is not executed

Javascript

blockOfCode: {
    console.log('This part will be executed');
    break blockOfCode;
    console.log('this part will not be executed');
}
console.log('out of the block');

Output

This part will be executed
out of the block

Example 4: labeled function declaration. myLabel is the label assigned to the function declaration. myLabeledFunction is the name of the function.

Javascript

myLabel: function myLabeledFunction() {
    console.log("This is a labeled function.");
}

// Calling the labeled function
myLabeledFunction();

Output

This is a labeled function.

Supported Browsers:

• Google Chrome
• Mozilla Firefox
• Microsoft Edge
• Safari