Why does this javaScript code create an infinite loop

Question

let i = 500;
do {
    if (isPrime(i) === false) {
        continue;
    } else {
        para.textContent += i + ', ';
    }
    i--;
} while (i >= 2);

and it works well if I moved the (i--) to the start of the loop.

Because isPrime(500) is false. PS no need to test x === false, just use !x. — jarmod
– jarmod, Commented Jun 8, 2020 at 19:33

Abhishek Bhagate · Accepted Answer · 2020-06-08 19:32:01Z

2

Your loop keeps iterating at -

if (isPrime(i) === false) {  //this condition will be true and code keeps looping because you never increment i
    continue;
}

But, in your code where you declare i-- at the beginning, i will keep decreasing no matter what. So the first one will run succesfully as expected, while in the second program, the execution will never go beyond the first if() condition.

answered Jun 8, 2020 at 19:32

Abhishek Bhagate

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Prakash Reddy Potlapadu · Accepted Answer · 2020-06-08 19:31:41Z

1

Initially i=500 , enter loop

if (isPrime(i) === false) {
        continue;
    }

this condition satisfies, and go to next iteration i value is 500 forever

answered Jun 8, 2020 at 19:31

Prakash Reddy Potlapadu

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