What are the mechanics of % in JavaScript?

Question

Here, it gives me the output of 0, 1, 2 just like the for loop except it only logs one number at a time.

I'm new to jQuery and I just stumbled across this line of code here. Can anyone explain the mechanic behind the working of this code? The thing that left me baffled is the third line of code.

var i = 0;
setInterval(() => {
  i = (i + 1) % 3;
  console.log(i);
}, 1000);

There's no jquery code there. Which part don't you understand? It's plain Javascript. — peeebeee, Dec 18 '18 at 09:00
As stated above, this is POJS. The things you may want to research are: arrow functions, setInterval and the modulo operator. 10 seconds in google for each of those and you'll have your answr — Rory McCrossan, Dec 18 '18 at 09:02
Possible duplicate of [What does % do in JavaScript?](https://stackoverflow.com/questions/8900652/what-does-do-in-javascript) — peeebeee, Dec 18 '18 at 09:28

score 0 · Answer 1 · answered Dec 18 '18 at 09:12

i = (i + 1) % 3; does two things

Increase i by 1
Use the modulo operator with argument 3 , This will result in every integer i to yield the values 0, 1, or 2, depenting on the remainder of the integer division (
1 % 3 = 1,
2 % 3 = 2,
3 % 3 = 0,
4 % 3 = 1,
5 % 3 = 2,
6 % 3 = 0,
etc.)

You could rewrite it to i++; i %= 3, if you wish to make these two steps more obvious. But this will not be necessary, as I assume any programmer will instantly understand the original line of code.

What are the mechanics of % in JavaScript?

1 Answers1