javascript - Can I change the "justify-content" value depending on the number of elements in the flex container?

Question

I am working on an image gallery on a legacy site. I can't use anything other than regular old HTML/jQuery or JS/CSS. I know this would be a lot easier with Bootstrap or some grid library.

I'm building it with flexbox. There are four images in each row, with multiple rows. It looks great when each row has its four images. When it has 2 or 3, because I am using justify-content: space-between, it makes it look weird because of the big gap between the images.

The reason I'm using space-between is that I want the images to align to the left of the parent container, and also to the right.

Some notes:

• Each flex item has a max-width of 150px
• I want a margin between items, but I don't care if this margin changes as the viewport width changes
• the flex container has a max width that only allows four 150px-wide items in a row

My question: if a row has less than a set # of elements (in this case four), can I change the justify-content to be something more appropriate, like flex-start?

Ideally, I want to do this without JavaScript/jQuery, but if that's impossible, I'm open to those solutions as well.

Also, feel free to let me know if I'm way overthinking this and don't even need to use justify-content: space-between. Here's a working example:

/* outer container */
.flex-container {
  padding: 24px 0;
  background: white;
  border: solid 1px rgba(0,0,0,.1);
  max-width: 700px; /* or whatever */
  
  /* flex props */
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
}

/* contains img block and title */
.thumb-grid {
  border: solid 1px rgba(0,0,0,.1);
  width: 150px;
  margin-bottom: 36px;
}

.thumb-grid:first-of-type { margin-left: 0; }
.thumb-grid:nth-of-type(4) { margin-right: 0; }

.thumb-grid p {
  text-align: center;
}

.img-block {
  background: black;
  height: 150px;
}

.img-block img {
  height: 150px;
  opacity: 1;
  transition: opacity 150ms;
}

.img-block:hover img {
  opacity: .9;
}

<div class="flex-container">
    
    <div class="thumb-grid">      
      <div class="img-block">        
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 1</p>      
    </div>
    
    <div class="thumb-grid">      
      <div class="img-block">        
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 2</p>      
    </div>
    
   <div class="thumb-grid">      
      <div class="img-block">        
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 3</p>      
    </div>
    
    <div class="thumb-grid">
      <div class="img-block">       
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 4</p>      
    </div>
    
    <div class="thumb-grid">      
      <div class="img-block">        
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 5</p>      
    </div>
    
    <div class="thumb-grid">      
      <div class="img-block">        
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 6</p>      
    </div>
    
   <div class="thumb-grid">      
      <div class="img-block">
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 7</p>      
    </div>
    
  </div>

Answer 1

Depending on what you need to support, it might make more sense to use CSS grid layouts (as TylerH pointed out, CSS Grids do not have universal browser support). Check the documentation for further info: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Grid_Layout

.flex-container {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 10px;
  grid-auto-rows: minmax(100px, auto);
}

<div class="flex-container">
    
    <div class="thumb-grid">      
      <div class="img-block">        
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 1</p>      
    </div>
    
    <div class="thumb-grid">      
      <div class="img-block">        
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 2</p>      
    </div>
    
   <div class="thumb-grid">      
      <div class="img-block">        
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 3</p>      
    </div>
    
    <div class="thumb-grid">
      <div class="img-block">       
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 4</p>      
    </div>
    
    <div class="thumb-grid">      
      <div class="img-block">        
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 5</p>      
    </div>
    
    <div class="thumb-grid">      
      <div class="img-block">        
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 6</p>      
    </div>
    
   <div class="thumb-grid">      
      <div class="img-block">
        <a href=""><img src="https://www.expedient.com/wp-content/uploads/2017/06/exp-mq-resouce-thumbnail-1-150x150.jpg" alt="example image"></a>        
      </div>      
      <p>Image 7</p>      
    </div>
    
  </div>