CODEWITHSUNDEEP
javascriptjqueryjquery-plugins
Naemy
Naemy

Reputation: 536

Only fire a function once on scroll (scrollstop)

So, I'd like to fire a function only once on scroll (using Scrollstop, given by a stackoverflow answer)

The problem is that I don't get to fire the function only once. I've tried different solutions ( .on(), setting a counter, setting it outside/inside the window.scrollstop function) but nothing worked.

I don't think it's difficult, but.. I didn't get to make it work so far.

Here's the plugin I'm using

  $.fn.scrollStopped = function(callback) {           
          $(this).scroll(function(){
              var self = this, $this = $(self);
              if ($this.data('scrollTimeout')) {
                clearTimeout($this.data('scrollTimeout'));
              }
              $this.data('scrollTimeout', setTimeout(callback,300,self));
          });
      };

and here's my code:

        $(window).scrollStopped(function(){
            if ($(".drawing1").withinViewport()) {      
                doNothing()
                }
            })


var doNothing = function() {
            $('#drawing1').lazylinepainter('paint');
        }

(removed the counter since it didn't work)

Live demo here

PS: the function I'd like to make happen only once is the lazyPaint. It begins when we scroll to the element but it fires once again when it ends.

Upvotes: 10

Views: 25787

Answers (5)

Jeremie
Jeremie

Reputation: 1028

The question is a bit old, but as it popped up first when I search for "addeventlistener scroll once", I will add this reply. There is now a { once: true } parameter to only trigger an event once.

window.addEventListener("scroll", () => {
/* your code here */
}, { once: true });

Upvotes: 0

Mike
Mike

Reputation: 1266

These anwsers didn't work for me so here's my code:

        var fired = 0;
        jQuery(this).scroll(function(){
            if(fired == 0){
                alert("fired");
                fired = 1;
            }
        });

Upvotes: 4

Jeemyeong Lee
Jeemyeong Lee

Reputation: 1

How about this solution?

function scrollEvent() {
  var hT = $('#scroll-to').offset().top,
    hH = $('#scroll-to').outerHeight(),
    wH = $(window).height(),
    wS = $(this).scrollTop();
  if (wS > (hT+hH-wH)){
    console.log('H1 on the view!');
    window.removeEventListener("scroll", scrollEvent);
  }
}
window.addEventListener("scroll", scrollEvent);

Upvotes: 0

hzhu
hzhu

Reputation: 3799

Here's my version of having a function fire once while listening to the scroll event:

var fired = false;
window.addEventListener("scroll", function(){
  if (document.body.scrollTop >= 1000 && fired === false) {
    alert('This will happen only once');
    fired = true;
  }
}, true)

Upvotes: 7

AddiktedDesign
AddiktedDesign

Reputation: 512

how about using a variable to see whether it was previously fired:

var fired = 0;
$.fn.scrollStopped = function(callback) {           
          $(this).scroll(function(){
              if(fired == 0){
                var self = this, $this = $(self);
                if ($this.data('scrollTimeout')) {
                  clearTimeout($this.data('scrollTimeout'));
                }
                $this.data('scrollTimeout', setTimeout(callback,300,self));
                fired = 1;
              }
          });
      };

Upvotes: 7

Related Questions