Question

I have a problem.

I need a Javascript function which increase (increment) variable value by 4, and when the variable value is 20, then set value of variable to 0 and again increment it by 4 and so on…

I think that I need for loop and if condition, but I don’t know how to implement this…

Example

the result must be:

x = 0; then x = 4, x = 8, x = 12, x = 16, x = 20, x = 0, x= 4 ….

Thank you

Answer 1

You can do this with a nested pair of loops:

while (true) {
    for (var x = 0; x <= 20; x += 4) {
        // use x
    }
}

This will be more efficient than using the mod (%) operator.

EDIT

From your comments, it sounds like you want to generate the sequence incrementally, rather than in a loop. Here’s a function that will return a function that will generate the next element of your sequence each time you call it:

function makeSequence() {
    var x = 20; // so it wraps to 0 first time
    return function() {
        if (x == 20) { x = 0 }
        else { x += 4 }
        return x;
    }
}

You could then use it like this (among many ways):

var sequence = makeSequence();

// and each time you needed the next element of the sequence:

var x = sequence();