JavaScript Do...While Loop

Syntax

do {
    // Code to execute
} while (condition);

In this syntax, the code block inside the do statement is executed first. After that, the condition is evaluated. If the condition is true, the code block runs again. This process continues until the condition evaluates to false.

Example: Basic Do...While Loop

let count = 0;

do {
    console.log('Count is: ' + count);
    count++;
} while (count < 5);

In this example, the loop will print the count value from 0 to 4. The code block inside the do statement runs first, then checks if the count is less than 5.

Key Features

• The do...while loop guarantees that the code block will execute at least once, regardless of the condition.
• This is useful when you need to ensure the execution of the code before checking a condition.

Use Case: Validating User Input

The do...while loop can be handy for validating user input until a valid value is entered.

let userInput;
do {
    userInput = prompt('Enter a number between 1 and 10:');
} while (userInput < 1 || userInput > 10);
console.log('Valid number entered: ' + userInput);

In this example, the user is repeatedly prompted to enter a valid number until they provide an acceptable input.

Conclusion

The do...while loop is a powerful control structure in JavaScript that allows for guaranteed execution of code at least once. Understanding its behavior is essential for scenarios where initial execution is necessary before evaluating a condition.