How to animate elements move with css3 transitions after hiding some element

Is it possible to animate elements move with css3 transitions after hiding some element using jQuery's .fadeOut()?

I found some kind of solution here (see "It works for grids, too" section):

However my case is more like this: http://jsfiddle.net/CUzNx/5/

<div class="container">
    <div id="item1" class="item">Test1</div>
    <div id="item2" class="item">Test2</div>
    <div id="item3" class="item">Test3</div>
    <div id="item4" class="item">Test4</div>
    <div id="item5" class="item">Test5</div>
    <div id="item6" class="item">Test6</div>
    <div id="item7" class="item">Test7</div>
</div>

<div style="clear:both">
<button onclick="$('#item1').fadeOut();">
   Hide first
</button>
<button onclick="$('#item1').fadeIn();">
   Show first
</button>
</div>

I have floating div elements and after some element is hidden, it would be nice if other elements were animated. Is it possible?

You could do something like this which uses a CSS class toggled by a little JavaScript and CSS transitions to do what you're looking for instead of using jQuery.

// The relevant CSS
.item {
    // Your original code here
    transition: 0.5s ease-in-out;
}
.hide {
    width: 0;
    height: 0;
    opacity: 0;
    margin: 0;
    padding: 0;
}

// The JavaScript
const items = document.getElementsByClassName('item');
for(let i = 0; i < items.length; i++) {
    items[i].addEventListener("click", function() {
        items[i].classList.toggle('hide');
    });
};

function addBack() {
    for(let i = 0; i < items.length; i++) {
        items[i].classList.remove('hide');
    }
}

I also took out your buttons and added an "Add all elements back" button:

<button onclick='addBack()'>Add all elements back</button>

If you're already using jQuery somewhere else in your project I also made this jQuery version. Here is the JavaScript for that:

function addBack() {
    $('.item').each(function() {
        $(this).removeClass('hide');
    });
}

$('.item').on('click', function() {
    $(this).toggleClass('hide');
});

Also, you don't need IDs for any of this, so they can be taken out if you so please.