2.2 - Do While

Review

• The While loop might never run, depending on the condition:

let raining = false;

while (raining) {

console.log("It's raining, I need an umbrella.");

}

// The loop above will not run. Not even once.

Notice that the while loop has the condition at the beginning.

Do While

• The do-while loop is similar, but it places the condition at the end of the loop.

let raining = false;

do {

console.log("It's raining! I need an umbrella.");

} while (raining);

In the above example, even though raining is false, we will still see the printout on the console. The check is at the end of the loop.

You might want to run the loop at least once. For example, getting user input.

let input;

do {

input = prompt("Please enter a number from 1 to 5");

input = Number(input);

} while ((isNaN(input)) || (input < 1) || (input > 5));

Notice that the variables raining and input were declared before the loops, not inside. This is crucial.