Difference between WHILE and DO WHILE loop

Loops are essential constructs in programming, allowing developers to execute a block of code repeatedly based on a condition. Two commonly used types of loops are the while loop and the do-while loop. Although they serve similar purposes, there are subtle differences between them that are crucial to understand. In this article, we’ll explore the differences between while and do-while loops in Typescript.

The While loop

The while loop is a pre-test loop, meaning it evaluates the condition before executing the loop's body. If the condition is false initially, the loop body will never execute. The syntax for a while loop is as follows:

while (condition) {
  // loop body
}

Example

The following example demonstrates a while loop that prints to the console the numbers from 1 to 5 using a counter variable:

let i: number = 1
 
while (i <= 5) {
  console.log(i)
  i++
}

The Do-While loop

The do-while loop is a post-test loop, meaning it evaluates the condition after executing the loop's body. This guarantees that the loop body will execute at least once, even if the condition is false initially. The syntax for a do-while loop is as follows:

do {
  // loop body
} while (condition)

Example

The following example demonstrates a do-while loop that prints to the console the numbers from 1 to 5 using a counter variable:

let i: number = 1
 
do {
  console.log(i)
  i++
} while (i <= 5)

Key Differences

Execution Guarantee

• while loop: The loop body will execute only if the condition is true initially.
• do-while loop: The loop body will execute at least once, even if the condition is false initially.

Pre-test vs. Post-test

• while loop: The condition is evaluated before executing the loop body.
• do-while loop: The condition is evaluated after executing the loop body.

Conclusion

Understanding the differences between while and do-while loops is fundamental for writing efficient and error-free code. Whether you choose a while loop for its simplicity and straightforwardness or a do-while loop for its guaranteed initial execution, selecting the right type of loop depends on the specific requirements of your program. By mastering these looping constructs, you enhance your ability to create robust and effective algorithms in your programs.