Literal Boolean Value in Loops

Question

I've seen this used a few times where a literal Boolean value is in the loop, like this...

while (true) { ... }

Prior to taking this course on JavaScript, I really haven't seen this used before in either Java, C#, or PHP. I'm wondering if this is a preferred method to using while and do...while loops because it's simpler and cleaner than using some Boolean variable that you can set to false in the loop block. Or maybe this is good to only use with JavaScript. Or maybe it's not a good practice to use at all and it's only been used for educational purposes right now. Can anyone clear this up for me? I'm always looking for ways to improve my code. Thanks.

Answer 1 · 2016-03-03T18:29:35Z

March 3, 2016 6:29pm

while(true){...} is usually used only as a learning tool on how to make your loop never stop running and eventually crash the browser.

In order to get a loop to run the conditional needs to be true. In order to get a loop to stop the conditional needs to be turned to false. Loop conditionals only accept a Boolean value, which can come in many forms. For example:

var count = 0;
while(count < 4) {
   console.log(count);
   count++;
}
/*
This while loop will continue to run (it's conditional is true) until the count
variable is 5.  Once count=5 the loop's condition will turn to false and the
loop will stop running.
*/
/*
There are things called truthy and falsy values.  It's easy to show the limited 
number of falsy values. Look at this example:
*/
function logTruthiness (val) {
  if (val) {
    console.log("Truthy!");
  } else {
     console.log("Falsy.");
   }
}

// Outputs: "Falsy."
logTruthiness(false);

// Outputs: "Falsy."
logTruthiness(null);

// Outputs: "Falsy."
logTruthiness(undefined);

// Outputs: "Falsy."
logTruthiness(NaN);

// Outputs: "Falsy."
logTruthiness(0);

// Outputs: "Falsy."
logTruthiness("");

// Outputs: "Truthy!"
logTruthiness(25);

You will use the for loop way more then the while loop. And you will commonly use the for..in loop for iterating through objects.

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Craig Fender

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Literal Boolean Value in Loops

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Julie Myers

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