The increment (++) and decrement (--) operators behave differently depending on where they are placed.

  • If used postfix (after), then it increments/decrements and returns the value BEFORE incrementing/decrementing
  • If used prefix (before), then it increments/decrements and returns the value AFTER incrementing/decrementing
let i = 0;
console.log(i++); // 0
console.log(i); // 1

let k = 0;
console.log(++k); // 1
console.log(k); // 1

let m = 0;
console.log(m--); // 0
console.log(m); // -1

let w = 0;
console.log(--w); // -1
console.log(w); // -1