Position last flex item at the end of container - css

Question

This question concerns a browser with full css3 support including flexbox.
I have a flex container with some items in it. They are all justified to flex-start but I want the last .end item to be justified to flex-end. Is there a good way to do this without modifying the HTML and without resorting to absolute positioning?
.container {
display: flex;
flex-direction: column;
outline: 1px solid green;
min-height: 400px;
width: 100px;
justify-content: flex-start;
}
p {
height: 50px;
background-color: blue;
margin: 5px;
}
<div class="container">
<p></p>
<p></p>
<p></p>
<p class="end"></p>
</div>

Answer 1

Flexible Box Layout Module - 8.1. Aligning with auto margins
Auto margins on flex items have an effect very similar to auto margins in block flow:
During calculations of flex bases and flexible lengths, auto margins are treated as 0.
Prior to alignment via justify-content and align-self, any positive free space is distributed to auto margins in that dimension.
Therefore you could use margin-top: auto to distribute the space between the other elements and the last element.
This will position the last element at the bottom.
p:last-of-type {
margin-top: auto;
}
.container {
display: flex;
flex-direction: column;
border: 1px solid #000;
min-height: 200px;
width: 100px;
}
p {
height: 30px;
background-color: blue;
margin: 5px;
}
p:last-of-type {
margin-top: auto;
}
<div class="container">
<p></p>
<p></p>
<p></p>
</div>
Likewise, you can also use margin-left: auto or margin-right: auto for the same alignment horizontally.
p:last-of-type {
margin-left: auto;
}
.container {
display: flex;
width: 100%;
border: 1px solid #000;
}
p {
height: 50px;
width: 50px;
background-color: blue;
margin: 5px;
}
p:last-of-type {
margin-left: auto;
}
<div class="container">
<p></p>
<p></p>
<p></p>
<p></p>
</div>

Answer 2

This flexbox principle also works horizontally
During calculations of flex bases and flexible lengths, auto margins
are treated as 0. Prior to alignment via justify-content and
align-self, any positive free space is distributed to auto margins in
that dimension.
Setting an automatic left margin for the Last Item will do the work.
.last-item {
margin-left: auto;
}
Code Example:
.container {
display: flex;
width: 400px;
outline: 1px solid black;
}
p {
height: 50px;
width: 50px;
margin: 5px;
background-color: blue;
}
.last-item {
margin-left: auto;
}
<div class="container">
<p></p>
<p></p>
<p></p>
<p class="last-item"></p>
</div>
Codepen Snippet
This can be very useful for Desktop Footers.
As Envato did here with the company logo.
Codepen Snippet