javascript / jquery - avoid repeating evaluation of a conditional

Question

I currently have a conditional running in jquery's scroll event, which doesn't seem to make a lot of sense since it will only execute once. I was wondering if there is any way to ensure that the conditional will only be evaluated once.

here's my code:

$window.scroll(function() {
  if (s1_doAnimate == true){
    s1_doAnimate = false;
  }
})

Is this a part of the code in scroll event or is this the only operation? — Karan Punamiya
– Karan Punamiya, Commented Aug 31, 2012 at 11:04

Maxim Krizhanovsky · Accepted Answer · 2012-08-31 11:09:37Z

3

Use $.one

$(window).one('scroll', function(){
...
});

answered Aug 31, 2012 at 11:09

Maxim Krizhanovsky

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Comments

Matt · Accepted Answer · 2012-08-31 11:07:10Z

2

You can unbind the handler once the condition has been met;

$window.scroll(function foo /* give the function a name */ () {
  if (s1_doAnimate == true){
    s1_doAnimate = false;

    // Unbind the handler referenced by the name...
    $window.off(foo);
  }
})

answered Aug 31, 2012 at 11:07

Matt

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2 Comments

David Hellsing Over a year ago

Wouldn’t this create a new function for each trigger? Maybe it’s better to store foo outside the handler? Just curious...

Matt Over a year ago

@David: No, the declaration is only processed once (before the function expression is passed to the scroll() function). IE < 9 will create 2 functions for it though (more);

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