Stop fixed block on last element - html

Question

I have the following snippet (open snippet as full page) :
#container_1{
margin-top: 50px;
margin-bottom: 150px;
}
.block1{
background: green;
margin-bottom: 15px;
color: #FFFFFF;
}
#moving_block{
z-index: 0;
background-color: purple;
color: #FFFFFF;
}
#footer{
background-color: gray;
height: 5000px;
color: #FFFFFF;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
<div id="container_1" class="container">
<div class="col-md-5 col-md-offset-1">
<div class="row block1">
<div class="col-md-8">
<p>TEXT</p>
</div>
</div>
<div class="row block1">
<div class="col-md-8">
<p>TEXT</p>
</div>
</div>
<div class="row block1">
<div class="col-md-8">
<p>TEXT</p>
</div>
</div>
<div class="row block1">
<div class="col-md-8">
<p>TEXT</p>
</div>
</div>
<div class="row block1">
<div class="col-md-8">
<p>TEXT</p>
</div>
</div>
</div>
<div class="col-md-4">
<div id="moving_block" class="col-md-3 affix">
<div class="row">
<p>TEXT</p>
</div>
</div>
</div>
</div>
<section id="footer">
MY FOOTER
</section>
I would like to stop the purple block when he encounter the last green block.

Answer 1

This can be done using position:sticky.
I consider bootstrap V4 for this since there is builtin function for sticky. I also simplified the code to keep only the relevant one for the demo:
#container_1 {
margin-top: 50px;
margin-bottom: 150px;
}
.block1 {
background: green;
color: #FFFFFF;
}
.block1:not(:last-child) {
margin-bottom: 15px;
}
#moving_block {
background-color: purple;
color: #FFFFFF;
}
#footer {
background-color: gray;
height: 5000px;
color: #FFFFFF;
}
<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css" rel="stylesheet">
<div id="container_1" class="container">
<div class="row">
<div class="col-5 col-offset-1">
<div class="row block1">
<p>TEXT</p>
</div>
<div class="row block1">
<p>TEXT</p>
</div>
<div class="row block1">
<p>TEXT</p>
</div>
<div class="row block1">
<p>TEXT</p>
</div>
<div class="row block1">
<p>TEXT</p>
</div>
</div>
<div class="col-6">
<div id="moving_block" class="overflow-auto position-sticky sticky-top">
<p>TEXT</p>
</div>
</div>
</div>
</div>
<section id="footer">
MY FOOTER
</section>