CODEWITHSUNDEEP
javascriptfunctionwhile-loopsettimeout
math
math

Reputation: 187

While loop, increasing a variable has no effect inside a setimeout function

I spent a lot of this time on this problem and finally I can show it in an easy to read code in jsfiddle: http://jsfiddle.net/Lb0g25ae/

function test(i) {
    return function() {
        console.log(i);
        //I need to increase valid here because this is where the script will choose wheter to increase or not (continue looping) valid depending on some conditions
    }
}

var valid = 0;
while (valid < 5) {
    setTimeout(test(valid), 1000*valid);
    valid++;
}

And I need it to be

function test(i) {
    return function() {
        console.log(i);
        valid++;
    }
}

var valid = 0;
while (valid < 5) {
    setTimeout(test(valid), 1000*valid);
}

But this way the loop won't stop, because valid is not being increased, this will produce an infinite loop and a crash. Someone can point me in the right direction?

Upvotes: 1

Views: 136

Answers (3)

gorpacrate
gorpacrate

Reputation: 5561

Valid doesn't increase because while cycle goes non-stop and overloads cpu immediately.

You need to call test after the timeout. Check:

var valid = 0;
function test() {
    console.log(valid);
    valid++;
    if(valid < 5){
        setTimeout(test, 1000*valid);
    }
}
test();

Upvotes: 3

BudgieInWA
BudgieInWA

Reputation: 2255

The issue here is that the while loop must run to completion before any of the timeouts can run. That is, valid will not be incremented until a second has passed and there is no other code running, but that will never happen because the while loop will still be running...

You need to schedule the following timeout inside the test function.

Upvotes: 0

QuinnFTW
QuinnFTW

Reputation: 554

The valid variable must be global, so try this

var valid = 0;
function test(i) {
    return function() {
        console.log(i);
        window.valid++;
    }
}


while (valid < 5) {
    setTimeout(test(valid), 1000*valid);
}

Upvotes: 0

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