CSS grid: different alignment for every second row

Question

Is it possible to align every second row right and every other left with CSS Grid? The number of .item is unknown.

Here is the HTML/CSS:

.container {
  grid-template-columns: repeat(4, 1fr);
}

<ul class="container">
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <!-- ... -->
</ul>

Expected solution:

I am open to other solutions than CSS Grid also.

Answer 1

A flexbox idea:

.container {
  display:flex;
  padding:0;
  margin:0;
  flex-wrap:wrap;
  border:1px solid red;
  --w:300px; /* the width of 4 items */
}

.container > * {
  flex-grow:1;
  flex-basis:calc(var(--w)/4);
  border:1px solid;
  box-sizing:border-box;
  list-style:none;
}

.container > *:nth-child(8n + 4) {
  margin-right:calc(100% - var(--w)); 
}
.container > *:nth-child(8n + 5) {
  margin-left:calc(100% - var(--w));
}

/* Irrelevant style to maintain the square ratio */
.container > *::before {
  content:"";
  display:inline-block;
  padding-top:100%;
}

<ul class="container">
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
</ul>

<ul class="container" style="--w:200px">
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
</ul>

<ul class="container" style="--w:60%">
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
</ul>

You can also use the old float method:

.container {
  padding:0;
  margin:0;
  border:1px solid red;
  overflow:auto;
  --w:300px; /* the width of 4 items */
}

.container > * {
  float:left;
  width:calc(var(--w)/4);
  border:1px solid;
  box-sizing:border-box;
  list-style:none;
}

.container > *:nth-child(8n + 5),
.container > *:nth-child(8n + 6),
.container > *:nth-child(8n + 7),
.container > *:nth-child(8n + 8){
  float:right;
}

.container > *:nth-child(8n + 5) {
  clear:left;
}
.container > *:nth-child(8n + 1) {
  clear:right;
}

/**/
.container > *::before {
  content:"";
  display:inline-block;
  padding-top:100%;
}
/**/

<ul class="container">
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
</ul>

<ul class="container" style="--w:200px">
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
</ul>

<ul class="container" style="--w:60%">
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
  <li class="item"></li>
</ul>

Answer 2

Possible with grid-column-start and grid-column-end property.

.container {
  display: inline-grid;
  grid-template-columns: repeat(6, 1fr);
  grid-auto-rows: auto;
  margin: 0;
  padding: 0;
}

.item {
  list-style: none;
  margin: 0;
  padding: 0;
  width: 100px;
  height: 100px;
  border: 1px solid red;
}

.item:nth-child(4) {
  grid-column-end: span 3;
}

.item:nth-child(8n + 5) {
  grid-column-start: 3;
}

<ul class="container">
  <li class="item">1</li>
  <li class="item">2</li>
  <li class="item">3</li>
  <li class="item">4</li>
  <li class="item">5</li>
  <li class="item">6</li>
  <li class="item">7</li>
  <li class="item">8</li>
  <li class="item">9</li>
  <li class="item">10</li>
  <li class="item">11</li>
  <li class="item">12</li>
  <li class="item">13</li>
  <li class="item">14</li>
  <li class="item">15</li>
  <li class="item">16</li>
</ul>

Answer 3

You can use nth-child() to create a repeating pattern.

ul {
  display: grid;
  grid-template-columns: repeat(6, 1fr);/* 6 = 4 + 2 empty cells */
  grid-auto-rows: 50px;/*demo purpose */
}

li {
  display: block;
  border: solid 1px;
}

li:nth-child(8n-3) {
  grid-column: 3;
}

li:nth-child(8n + 1) {
  grid-column: 1
}

/*demo purpose */
ul{counter-reset:lis;}
li:before {counter-increment:lis;content:counter(lis);}

<ul>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
  <li></li>
</ul>