Given the following function:
let ticks = 0;
let clock = setInterval(() => {
console.log("tick", ticks++);
if (ticks == 10) {
clearInterval(clock);
console.log("stop.");
}
}, 200);Why is the first thing logged to the console "tick 0" rather than "tick 1", since it is immediately incrementing ticks by 1 (ticks++)? Or, is it the case that JS sees "ticks" first and immediately logs that, then sees the ++ and increments it accordingly?
ticks++ evaluates to ticks, and after that, adds 1. You probably want ++ticks.
It jumps at you right at the start of the documentation of the ++ operator:
If used postfix, with operator after operand (for example,
x++), the increment operator increments and returns the value before incrementing.
If used prefix, with operator before operand (for example,++x), the increment operator increments and returns the value after incrementing.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Increment#description