Javascript while loop conditions

Question

The following javascript fragment goes into an infinite loop. Why is that?

 var playerChoice=prompt("Choose paper or rock or scissors"); 
 while (playerChoice !=="paper" || playerChoice !=="rock" || playerChoice !== "scissors"){   
       playerChoice=prompt("Choose paper or rock or scissors"); 
 }

@Minhajraz != vs !== shouldn't make a difference here. Have you tried switching to using && instead of || as per the various answers? — James Thorpe
– James Thorpe, Commented May 6, 2015 at 9:40

James Thorpe · Accepted Answer · 2015-05-06 09:22:23Z

4

Because when a new choice is made, it will always match at least two of the conditions, and since you've used the OR (||) operator, will continue with the loop. You need to use the AND (&&) operator instead:

var playerChoice=prompt("Choose paper or rock or scissors");

while (playerChoice !=="paper" && playerChoice !=="rock" && playerChoice !== "scissors"){
    playerChoice=prompt("Choose paper or rock or scissors"); 
}

Now when a valid choice is made, two of the 3 inner conditions are still met, but because the last one isn't, the whole condition will evaluate to false and the loop will not execute.

answered May 6, 2015 at 9:22

James Thorpe

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1 Comment

Minhajraz Over a year ago

Thanks for explanations @james Thorpe.

Arun P Johny · Accepted Answer · 2015-05-06 09:32:54Z

2

You need to use &&. You need to quit the loop if the choice is either one of the valid choices

while (playerChoice != "paper" && playerChoice != "rock" && playerChoice != "scissors") {
    playerChoice = prompt("Choose paper or rock or scissors");
}

Demo: Fiddle

In your case assume, playerChoice is paper but when evaluating your condition playerChoice !=="rock" is true and since you have used || if any of the condition is true the loop will get executed

edited May 6, 2015 at 9:32

answered May 6, 2015 at 9:21

Arun P Johny

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6 Comments

Paul Fitzgerald Over a year ago

The issue is with the !=, is it not?

Minhajraz Over a year ago

I thought && will only return 'true' if all the values are true. I want it to return true if either case is true

James Thorpe Over a year ago

@PaulFitzgerald See the Strict Inequality operator vs the Inequality operator. !== is perfectly valid.

T.J. Crowder Over a year ago

@PaulFitzgerald: No, it isn't.

Minhajraz Over a year ago

Any one with any other idea?? I am stack here!

|

OTTA · Accepted Answer · 2015-05-06 09:23:49Z

0

You're using OR where you should be using AND, whether Rock, Paper or Scissors is entered two of your conditions will evaluate as TRUE so you'll go around the loop again, and again, and again.....

answered May 6, 2015 at 9:23

OTTA

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