Setting equal heights for div's with jQuery

Answer to your specific question

Your code was checking all columns within any container, what you need to do is:

• Loop through each container
  • Get the heights of each column within that container
  • Find the highest one
  • Apply that height to every column in that container before moving on to the next one.

Note: Try to provide an example jsfiddle of your issue, it enables us to more easily help you and understand the issue, you get to see the working solution straight away and it encourages quicker responses.

Quick (Rough) Example

$(document).ready(function(){

    // Select and loop the container element of the elements you want to equalise
    $('.container').each(function(){  
      
      // Cache the highest
      var highestBox = 0;
      
      // Select and loop the elements you want to equalise
      $('.column', this).each(function(){
        
        // If this box is higher than the cached highest then store it
        if($(this).height() > highestBox) {
          highestBox = $(this).height(); 
        }
      
      });  
            
      // Set the height of all those children to whichever was highest 
      $('.column',this).height(highestBox);
                    
    }); 

});

.container { border 1px solid red; }
.column { border: 1px solid blue; float:left; width: 30%; text-align:center; }

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>

<div class="container">
    <div class="column">This is<br />the highest<br />column</div>
    <div class="column">One line</div>
    <div class="column">Two<br />lines</div>
</div>
<div class="container">
    <div class="column">One line</div>
    <div class="column">Two<br>lines</div>
    <div class="column">One line</div>
</div>

Library!

Here's a library i found that looks promising if you want some more clever equalisation controls

http://brm.io/jquery-match-height-demo/

Addressing @Mem's question

Question: Will $(document).ready() work if you have images that need to load which in turn modify the heights of the containers?

Equalising heights after image load

If you are loading images, you will find that this solution doesn't always work. This is because document.ready is fired at the earliest possible time, which means it does not wait for external resources to be loaded in (such as images).

When your images finally load, they may distort the heights of their containers after the equalisation script has run, causing it too appear not too work.

Solving equalising heights with images

1. Bind to image loading events

This is the best solution (at the time of writing) and involves binding to the img.load event. All you have to do is get a count of how many img's there are $('img').length and then for each load, -1 from that count until you hit zero, then fire the equaliser.

The caveat here is load may not fire in all browsers if the image is in the cache. Look around google/github, there should be a solution script out there. At the time of writing i found waitForImages from Alexander Dickson (untested, this is not an endorsement).

2. Another more reliable solution is the window.load event. This should generally always work. However, if you check the docs out, you'll notice this event fires after ALL external resources are loaded. This means if your images are loaded but there's some javascript waiting to download it won't fire until that completes.

If you load the majority of your externals asyncronously and are clever with minimising, compressing and spreading the load you probably wont have any issues with this method, however a suddenly slow CDN (happens all the time) could cause issues.

In both cases, you could take a dumb approach and apply fallback timers. Have the equalise script run automatically after a set few seconds just in case the event doesn't fire or something is slow out of your control. It's not fool proof, but in reality you'll satisfy 99% of your visitors with this fallback if you tune the timer correctly.

Years later this is still getting upvotes, with flexbox widely supported these days you may want to consider just plain CSS for this, unless there's a specific reason you are using JS for it

.container {
  display: flex;
  border: 2px dashed red;
  margin: 10px 0;
}

.container > .column { 
 padding: 10px;
}

.container.fill-width {
  justify-content: stretch;
}

.container.fill-width>.column {
  flex-grow: 1
}

.container>.column:nth-child(1) {
  background: yellow;
}

.container>.column:nth-child(2) {
  background: blue;
}

.container>.column:nth-child(3) {
  background: green;
}

<div class="container">
  <div class="column">Some<br>text</div>
  <div class="column">Some<br>more<br>text<br>here</div>
  <div class="column">One line</div>
</div>
<div class="container">
  <div class="column">Some<br>more<br>even<br>longer<br>text<br>here</div>
  <div class="column">Some<br>text</div>
  <div class="column">One line</div>
</div>
<div class="container fill-width">
  <div class="column">Some<br>more<br>text<br>here</div>
  <div class="column">Some<br>text</div>
  <div class="column">One line</div>
</div>

$(document).ready(function(){

    $('.container').each(function(){  
        var highestBox = 0;

        $(this).find('.column').each(function(){
            if($(this).height() > highestBox){  
                highestBox = $(this).height();  
            }
        })

        $(this).find('.column').height(highestBox);
    });    


});

You need this:

$('.container').each(function(){  
     var $columns = $('.column',this);
     var maxHeight = Math.max.apply(Math, $columns.map(function(){
         return $(this).height();
     }).get());
     $columns.height(maxHeight);
});

Explanation

• The following snippet constructs an array of the heights:

  $columns.map(function(){
      return $(this).height();
  }).get()
  

• Math.max.apply( Math, array ) finds the maximum of array items

• $columns.height(maxHeight); sets all columns' height to maximum height.

Live demo