[SOLVED] NaN error

Question

In this code, why does 'inc' return Not a Number, yet 'deltatime' doesn't? All I did was add deltatime to inc!
😢

var time_0=0;
var inc=0;
var deltatime;
function update(timestamp){
deltatime=timestamp-time_0;
inc+=deltatime;
console.log(inc,deltatime);
time_0=timestamp;
window.webkitRequestAnimationFrame(update);
}
update();

Try it yourself
https://code.sololearn.com/WTF3c76tSa6s/#html

Answer 1

Théophile but why doesn't timechange return NaN yet it's also dependent on the timestamp parameter?

Answer 2

Do your first call to your 'update' function through a requestAnimationFrame call:

var time_0=0;
var inc=0;
var deltatime;
function update(timestamp){
deltatime=timestamp-time_0;
inc+=deltatime;
console.log(inc,deltatime);
time_0=timestamp;
window.webkitRequestAnimationFrame(update);
}
window.webkitRequestAnimationFrame(update);

Anyway, webkitRequestAnimationFrame is browser vendor prefixed and should only work in webkit based browsers ^^

Answer 3

visph that works. It also works when I supply time_0 as the argument when I call update()

Answer 4

How timestamp is initialized ?
I don;t know js but what about try inside the function

timestamp = Date.now();

Answer 5

Your update function takes one parameter : if you give None, 0+none=Nan

Answer 6

Your function update returns undefined because it's looking for a function update without parameter...

Answer 7

I don't know why it returns undefined and not Nan...