egedraw rainbow

function rgbtohex(r,g,b) {
    if (isNaN(r) || isNaN(g) || isNaN(b)) return;
    r = parseInt(r);
    g = parseInt(g);
    b = parseInt(b);
    return "#"+(r.toString(16)+g.toString(16)+b.toString(16)).padStart(6,0);
};
var f = 0.009;
var i = 0;
var drw = draw;
draw = function(e) {
    drw(e);
    var j = 255/2; /* idk what to call this variable */
    var red = Math.sin(f*i + 4) * j + j;
    var green = Math.sin(f*i + 2) * j + j;
    var blue = Math.sin(f*i) * j + j;
    colorPicker.value = rgbtohex(red,green,blue);
    localStorage.setItem('color', colorPicker.value);
    i++
};