scroll-breakpoint.js

Plugin aimed for reducing the overhead on a client side for scroll event handling. In most cases we have to do some actions on exact breakpoint and continue scrolling the page, but many developers forget to check that actions has been performed and repeating them on every single event.

Usage

Let's add the sticky-header class to the body element as soon as scroll position will be below of 500 pixels and remove it otherwise.

window.scrollBreakpoint(function() {
  return this.scrollY > 500;
}, function(isTrue) {
  // This code will be executed exactly once when you'll reach the breakpoint.
  document.body.classList[isTrue ? 'add' : 'remove']('sticky-header');
});

One bad example which I'm seeing all the time:

window.addEventListener('scroll', function() {
  // This code will be executed every time during page scrolling.
  document.body.classList[this.scrollY > 500 ? 'add' : 'remove']('sticky-header');
});

The result of two samples above will be completely the same. Customer will not see the difference. But in the first case, class to the body will be added as soon as page will be scrolled to 500 pixels or below and removed when scroll location will be above of this height. In second one - the same actions will be performed every f***ing scroll. Check the demonstration and see by yourself.