In JavaScript, a "while" loop will execute a block of code repeatedly as long as a given condition is true. On the other hand, a "do-while" loop will execute a block of code once, and then repeatedly as long as a given condition is true.
The main difference between the two is that the code in a "do-while" loop will always execute at least once, whereas the code in a "while" loop may never execute if the condition is initially false.
While loop
A while loop in JavaScript is a control flow statement that allows you to execute a block of code repeatedly as long as a given condition is true. The syntax for a while loop is as follows:
while (condition) {
// code block to be executed
}The code block inside the while loop will be executed repeatedly as long as the condition specified in the while statement is true. If the condition is initially false, the code block inside the while loop will not be executed at all.
For example, the following while loop will print the numbers from 1 to 5:
let i = 1;
while (i <= 5) {
console.log(i);
i++;
}Do-while loop
On the other hand, a do-while loop is similar to a while loop, but the code block inside the loop is executed at least once, regardless of whether the condition specified in the while statement is true or false. The syntax for a do-while loop is as follows:
do {
// code block to be executed
} while (condition);The code block inside the do-while loop will be executed once, and then the condition specified in the while statement will be evaluated. If the condition is true, the code block inside the loop will be executed again. The loop will continue to execute as long as the condition is true.
For example, the following do-while loop will prompt the user for their name and will continue to prompt them until they enter a name:
let name;
do {
name = prompt("What is your name?");
} while (!name);It will execute the prompt() function at least once even if the user enters an empty string, but the loop will end once the user enters a name.
It's important to note that while loops and do-while loops can both be used to create infinite loops if the condition specified in the while statement is always true. An infinite loop is a loop that continues to execute indefinitely, and can cause a program to hang or crash if not properly handled. To avoid infinite loops, it is important to include a way to change the value of the condition within the code block so that it eventually becomes false.
Additionally, while loops and do-while loops can both be used to execute a block of code a specific number of times. By using a counter variable and incrementing it within the code block, you can specify a specific number of iterations for the loop.
In summary, the main difference between while and do-while loops in JavaScript is that the code inside a "while" loop may never execute if the condition is initially false, whereas the code inside a "do-while" loop will always execute at least once before the condition is evaluated. Both loops can be used to execute a block of code repeatedly as long as a given condition is true, but the "do-while" loop guarantees that the code block will be executed at least once.