conditional-breakpoint.js

Plugin aimed at reducing the overhead on a client side in the handling of scroll and resize events. In most cases we have to do some actions on an exact breakpoint and continue scrolling/resizing the page, but many developers forget to check that actions have been performed and repeating them on every single event occasion.

Browsers support

Every browser that has window.addEventListener() is supported (IE9+).

Installation

Bower

bower install conditional-breakpoint

NPM

npm install conditional-breakpoint

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.conditionalBreakpoint.scroll(function() {
  return this.scrollY > 500;
}, function(isTrue) {
  // This code will be executed exactly once when you'll reach the
  // breakpoint and not as many times as event will be fired.
  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 a page will be scrolled to 500 pixels or below and removed when scroll location will be above of this height. In the second one - the same actions will be performed every f***ing scroll. Check the demonstration and see personally.

The same technique can be used for handling the resize event. Check it out:

window.conditionalBreakpoint.resize(function() {
  return this.innerWidth > 500;
}, function(isTrue) {
  // This code will be executed exactly once when the window width
  // is bigger than 500 pixels.
  document.body.classList[isTrue ? 'add' : 'remove']('sticky-header');
});

And its bad brother:

window.addEventListener('resize', function() {
  var isTrue = this.innerWidth > 500;
  // Execute one of the methods as many times as the event is fired. Gosh...
  document.body.classList[isTrue ? 'add' : 'remove']('sticky-header');
});