javascript i++ vs ++i [duplicate]

In javascript I have seen i++ used in many cases, and I understand that it adds one to the preceding value:

for (var i=1; i<=10; i++) {
  console.log(i);
}

But what happens when I do this:

++i;

And is it any different using the -- operator (besides of course that it's subtraction rather than addition)?

The difference between i++ and ++i is the value of the expression.

The value i++ is the value of i before the increment. The value of ++i is the value of i after the increment.

Example:

var i = 42;
alert(i++); // shows 42
alert(i); // shows 43
i = 42;
alert(++i); // shows 43
alert(i); // shows 43

The i-- and --i operators works the same way.

++variable increments the variable, returning the new value.

variable++ increments the variable, but returns the old value.

--variable decrements the variable, returning the new value.

variable-- decrements the variable, but returns the old value.

For example:

a = 5;
b = 5;
c = ++a;
d = b++;

a is 6, b is 6, c is 6 and d is 5.

If you're not using the result, the prefix operators work equally to the postfix operators.

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