don't re-assign variable reloading script

Question

I have a script in JavaScript which is called several times in a html page. I want to know how it's possible to assign values to a variable only the first call of the script.

var processingYear = 0;
var recupMonth = 0;
var recupYear = 0;


if(processingMonth == startMonth && processingYear == startYear && recupMonth == 0 && recupYear == 0){
            recupMonth = startMonth;
            recupYear = startYear;
        }

Even the declarations are called again and again? – Hanky Panky Oct 30 '13 at 13:19 — Hanky Panky, Oct 30 '13 at 13:19
You should include the script just once, and use functions. – SLaks Oct 30 '13 at 13:20 — SLaks, Oct 30 '13 at 13:20

Szymon Drosdzol · Answer 1 · 2013-10-30T13:26:15.613

3

var processingYear = processingYear || 0;

edited Oct 30 '13 at 13:26

answered Oct 30 '13 at 13:20

Szymon Drosdzol

469
3
13

1

It should be `var processingYear = processingYear || 0;` – Tibos Oct 30 '13 at 13:25
@Tibos Bitwise OR (`|`) should work too, but only on `Number` types. – azz Oct 30 '13 at 13:27
@Der Flatulator `1|2 === 3`. I'm quite sure that's not what you had in mind. – Tibos Oct 30 '13 at 13:29
@Tibos, only with `0`. `n | 0 === n`, or `0` if n is undefined. – azz Oct 30 '13 at 13:32

score 3 · Accepted Answer · answered Oct 30 '13 at 13:23

If i understand correctly you want to include the same script multiple times in the same HTML page. To prevent the script from overwriting your initializations, you can simply check if the variables have values before redefining them:

Instead of:

var x = 2;

Do:

var x = (x !== undefined) ? x : 2;

A shorter version would be var x = x || 2;, but that can backfire if your x variable holds a value that is evaluated to false (for example 0) after the script is executed.

score 0 · Answer 3 · answered Oct 30 '13 at 13:32

0

window.count ? count="defined" : count="undefined";
if(count=="undefined"){
  var processingYear = 0;
  var recupMonth = 0;
  var recupYear = 0;
}

Just another way to do !

answered Oct 30 '13 at 13:32

sakthi

929
6
18

don't re-assign variable reloading script

3 Answers3