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While Loops

Q: What is the main difference between while and do-while?

Answer: A while loop checks the condition before executing the code block. A do-while loop executes the code block first and then checks the condition, meaning it always runs at least once..

Q: When should you use a while loop instead of a for loop?

Answer: Use a for loop when you know exactly how many times you want to loop (e.g., length of an array). Use a while loop when you want to loop until a certain condition is met, but you don't know when that will happen..

Q: What happens if the condition in a while loop is always true?

Answer: It creates an infinite loop, which will consume 100% of the CPU thread and eventually cause the browser or environment to become unresponsive..

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Expert Answer & Key Takeaways

Mastering While Loops is essential for high-fidelity technical architecture and senior engineering roles in 2026.

JavaScript While Loops

While loops execute a block of code as long as a specified condition is true. They are ideal when the number of iterations is not known beforehand.

1. The While Loop

The while loop loops through a block of code as long as a specified condition is true.

while (condition) {
  // code block to be executed
}

Example:

let i = 0;
while (i < 10) {
  console.log("The number is " + i);
  i++;
}

[!CAUTION] If you forget to increment the variable used in the condition, the loop will never end. This will crash your browser tab.

2. The Do While Loop

The do while loop is a variant of the while loop. This loop will execute the code block once, before checking if the condition is true, then it will repeat the loop as long as the condition is true.

do {
  // code block to be executed
} while (condition);

Example:

let i = 0;
do {
  console.log("The number is " + i);
  i++;
} while (i < 10);

The code above will always be executed at least once, even if the condition is false, because the code block is executed before the condition is tested.

While Loops

Expert Answer & Key Takeaways

JavaScript While Loops

1. The While Loop

2. The Do While Loop

Top Interview Questions

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While Loops

Expert Answer & Key Takeaways

JavaScript While Loops

1. The While Loop

2. The Do While Loop

Top Interview Questions

?Interview Question

?Interview Question

?Interview Question

Course4All Engineering Team

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