jQuery on window resize

Question

Here's an example using jQuery, javascript and css to handle resize events.
(css if your best bet if you're just stylizing things on resize (media queries))
http://jsfiddle.net/CoryDanielson/LAF4G/

css

.footer 
{
    /* default styles applied first */
}

@media screen and (min-height: 820px) /* height >= 820 px */
{
    .footer {
        position: absolute;
        bottom: 3px;
        left: 0px;
        /* more styles */
    }
}

javascript

window.onresize = function() {
    if (window.innerHeight >= 820) { /* ... */ }
    if (window.innerWidth <= 1280) {  /* ... */ }
}

jQuery

$(window).on('resize', function(){
    var win = $(this); //this = window
    if (win.height() >= 820) { /* ... */ }
    if (win.width() >= 1280) { /* ... */ }
});

How do I stop my resize code from executing so often!?

This is the first problem you'll notice when binding to resize. The resize code gets called a LOT when the user is resizing the browser manually, and can feel pretty janky.

To limit how often your resize code is called, you can use the debounce or throttle methods from the underscore & lodash libraries.

• debounce will only execute your resize code X number of milliseconds after the LAST resize event. This is ideal when you only want to call your resize code once, after the user is done resizing the browser. It's good for updating graphs, charts and layouts that may be expensive to update every single resize event.
• throttle will only execute your resize code every X number of milliseconds. It "throttles" how often the code is called. This isn't used as often with resize events, but it's worth being aware of.

If you don't have underscore or lodash, you can implement a similar solution yourself: JavaScript/JQuery: $(window).resize how to fire AFTER the resize is completed?

Move your javascript into a function and then bind that function to window resize.

$(document).ready(function () {
    updateContainer();
    $(window).resize(function() {
        updateContainer();
    });
});
function updateContainer() {
    var $containerHeight = $(window).height();
    if ($containerHeight <= 818) {
        $('.footer').css({
            position: 'static',
            bottom: 'auto',
            left: 'auto'
        });
    }
    if ($containerHeight > 819) {
        $('.footer').css({
            position: 'absolute',
            bottom: '3px',
            left: '0px'
        });
    }
}

Try this solution. Only fires once the page loads and then during window resize at predefined resizeDelay.

$(document).ready(function()
{   
   var resizeDelay = 200;
   var doResize = true;
   var resizer = function () {
      if (doResize) {

        //your code that needs to be executed goes here

        doResize = false;
      }
    };
    var resizerInterval = setInterval(resizer, resizeDelay);
    resizer();

    $(window).resize(function() {
      doResize = true;
    });
});

jQuery has a resize event handler which you can attach to the window, .resize(). So, if you put $(window).resize(function(){/* YOUR CODE HERE */}) then your code will be run every time the window is resized.

So, what you want is to run the code after the first page load and whenever the window is resized. Therefore you should pull the code into its own function and run that function in both instances.

// This function positions the footer based on window size
function positionFooter(){
    var $containerHeight = $(window).height();
    if ($containerHeight <= 818) {
        $('.footer').css({
            position: 'static',
            bottom: 'auto',
            left: 'auto'
        });
    }
    else {
        $('.footer').css({
            position: 'absolute',
            bottom: '3px',
            left: '0px'
        });
    } 
}

$(document).ready(function () {
    positionFooter();//run when page first loads
});

$(window).resize(function () {
    positionFooter();//run on every window resize
});

See: Cross-browser window resize event - JavaScript / jQuery

Give your anonymous function a name, then:

$(window).on("resize", doResize);

http://api.jquery.com/category/events/

function myResizeFunction() {
  ...
}

$(function() {
  $(window).resize(myResizeFunction).trigger('resize');
});

This will cause your resize handler to trigger on window resize and on document ready. Of course, you can attach your resize handler outside of the document ready handler if you want .trigger('resize') to run on page load instead.

UPDATE: Here's another option if you don't want to make use of any other third-party libraries.

This technique adds a specific class to your target element so you have the advantage of controlling the styling through CSS only (and avoiding inline styling).

It also ensures that the class is only added or removed when the actual threshold point is triggered and not on each and every resize. It will fire at one threshold point only: when the height changes from <= 818 to > 819 or vice versa and not multiple times within each region. It's not concerned with any change in width.

function myResizeFunction() {
  var $window = $(this),
      height = Math.ceil($window.height()),
      previousHeight = $window.data('previousHeight');

  if (height !== previousHeight) {
    if (height < 819)
      previousHeight >= 819 && $('.footer').removeClass('hgte819');
    else if (!previousHeight || previousHeight < 819)
      $('.footer').addClass('hgte819');

    $window.data('previousHeight', height);
  }
}

$(function() {
  $(window).on('resize.optionalNamespace', myResizeFunction).triggerHandler('resize.optionalNamespace');
});

As an example, you might have the following as some of your CSS rules:

.footer {
  bottom: auto;
  left: auto;
  position: static;
}

.footer.hgte819 {
  bottom: 3px;
  left: 0;
  position: absolute;
}