Difference between - var+1 and var++

Question

im wondering, why int++ is not working, but int+1 is working. Someone have an idea why this happend in my example? Is there any difference?

function retryFunction(something, count) {
     if (!count) {
         count = 0;
     }

     console.log(typeof count);
     console.log(count);

     if (count < 5) {
          return setTimeout(function () {
              //working
              retryFunction(something, count+1);

              //not working
              retryFunction(something, count++);
          }, 1000)
      }
}

retryFunction(null);

(whatever "not working" means) because in the second case `count` is incemented *after* the call. — Federico klez Culloca, Feb 22 '18 at 13:48
Possible duplicate of [What is the difference between "++" and "+= 1 " operators?](https://stackoverflow.com/questions/12988140/what-is-the-difference-between-and-1-operators) — Phiter, Feb 22 '18 at 13:50
Possible duplicate of [Why doesn't the shorthand arithmetic operator ++ after the variable name return 2 in the following statement?](https://stackoverflow.com/questions/11218299/why-doesnt-the-shorthand-arithmetic-operator-after-the-variable-name-return) — Sohaib Shabbir بٹ, Feb 22 '18 at 13:55

score 5 · Answer 1 · answered Feb 22 '18 at 13:49

5

The expression count + 1 adds 1 to count and "returns" the result of that.

The expression count++ returns the current value of count, and then adds 1 to count (thereby modifying the variable value, but after the old value was used).

answered Feb 22 '18 at 13:49

Some programmer dude

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1

`count + 1` also can be written as `++count` – semanser Feb 22 '18 at 13:54
2

@semanser Except it doesn't do the same thing. `count + 1` doesn't modify `count`, while `++count` does. – Some programmer dude Feb 22 '18 at 14:05
You may add this your answer. Here is also a little example on [TIO](https://tio.run/##y0osSyxOLsosKNHNy09J/f@/LLFIITm/NK9EwVbBwJorOT@vOD8nVS8nP11DWxssoYkqilNMW5tolYbYVf7/DwA "JavaScript (Node.js) – Try It Online") which demonstrate this. – Martin Backasch Feb 22 '18 at 14:08
@Some programmer dude Generally yes, but not in the case of OP. – semanser Feb 22 '18 at 14:09

score 2 · Answer 2 · answered Feb 22 '18 at 13:53

Prefix increment vs. postfix increment operator. Speaking loosely in the context of your example, count++ says "call the function with the original value, then increment and store in the variable". If you were however to use ++count, this says "increment the variable and send the result to the function."

NB. Whilst ++count would "work", what you actually want is count + 1; it makes no sense to store the result in the passed parameter in this context.

Difference between - var+1 and var++

2 Answers2