Evan Miller source code for sample size from my blog post http://www.alfredo.motta.name/ab-testing-from-scratch/

gistfile1.txt

function num_subjects(alpha, power_level, p, delta) {
    var t_alpha2 = ppnd(1.0-alpha/2);
    var t_beta = ppnd(power_level);

    var sd1 = Math.sqrt(2 * p * (1.0 - p));
    var sd2 = Math.sqrt(p * (1.0 - p) + (p + delta) * (1.0 - p - delta));

    return (t_alpha2 * sd1 + t_beta * sd2) * (t_alpha2 * sd1 + t_beta * sd2) / (delta * delta);
}

This is missing from the part before the declaration of t_alpha2, see https://www.evanmiller.org/ab-testing/sample-size-fixed.js

if (p > 0.5) {
        p = 1.0 - p;
}

this is for relative delta. Is there a way to calculate sample size for absolute delta?
thank you