How can I reverse flex direction for each row?

Issue

I'm trying to see if this is possible with flexbox. I'm trying to accomplish 2 things:

1. Have div container width be 60% and another 40% (so only 2 items per row making 100%)
2. Each row will reverse (so first row is 60%/40%, then next row would be 40%/60%)

My setup is as follows (The items will always be equal so in this case 6 items, a total of 3 rows)

.ImageContainer {
  display: flex;
  flex-wrap: wrap;
}

.ImageItem {
  border:1px solid #000000;
}

.ImageItem:nth-child(even) {
  width: 60%;
}

.ImageItem:nth-child(odd) {
  width: 40%;
}

<div class="ImageContainer">
  <div class="ImageItem">1</div>
  <div class="ImageItem">2</div>
  <div class="ImageItem">3</div>
  <div class="ImageItem">4</div>
  <div class="ImageItem">5</div>
  <div class="ImageItem">6</div>
</div>

Solution

Use selectors as follows for the flex children. The ":nth-child(4n+x)" will select the children in steps of four with the corresponding "x" offset:

html,
body {
  margin: 0;
}

.ImageContainer {
  display: flex;
  flex-wrap: wrap;
  width: 100%;
}

.ImageItem {
  border: 1px solid #ccc;
  height: 60px;
  box-sizing: border-box;
}

.ImageItem:nth-child(4n+1),
.ImageItem:nth-child(4n+4) {
  width: 60%;
}

.ImageItem:nth-child(4n+2),
.ImageItem:nth-child(4n+3) {
  width: 40%;
}

<div class="ImageContainer">
  <div class="ImageItem"></div>
  <div class="ImageItem"></div>
  <div class="ImageItem"></div>
  <div class="ImageItem"></div>
  <div class="ImageItem"></div>
  <div class="ImageItem"></div>
  <div class="ImageItem"></div>
  <div class="ImageItem"></div>
  <div class="ImageItem"></div>
  <div class="ImageItem"></div>
</div>

Answered By - Johannes