Can flexbox detect when a flex item wraps?

问题:

I am hoping to get rid of media queries and just use flexbox to solve my problem, but I'm not sure if this is possible. As the window gets smaller, I want the columns to shrink until they hit their minimum width. Once they hit that, the middle column will jump down for the wrap.

I think my question boils down to this- can flexbox detect when it wraps? If so, can I prompt it to change the order of the items on wrap with strictly CSS?

Here is a codepen of what I"m trying to accomplish using media queries.

.wrapper {
  display: flex;
  justify-content: center;
  margin: 5px;
  flex-wrap: wrap;
}

.red {
  background-color: red;
  height: 240px;
  margin: 5px;
  width: 500px;
  order: 0;
}

.yellow {
  background-color: yellow;
  margin: 5px;
  height: 240px;
  min-width: 240px;
  max-width: 400px;
  flex: 1;
  order: 1;
}

.blue {
  background-color: blue;
  height: 240px;
  margin: 5px;
  min-width: 350px;
  max-width: 400px;
  flex: 1;
  order: 2;
}

@media (max-width:1130px) {
  .yellow {
    order: 4;
  }
}

<div class="wrapper">
  <div class="red"></div>
  <div class="yellow"></div>
  <div class="blue"></div>
</div>

回答1:

Can flexbox detect when a flex item wraps?

No.

In CSS, once the browser renders the page on the initial cascade, it doesn't reflow the document when an element wraps. As a result, parent elements don't know when their children wrap.

That's why containers don't shrink-to-fit their content after wrapping.

That's why you need media queries or JavaScript.

Here are some more details:

• Make container shrink-to-fit child elements as they wrap
• How to center a flex container but left-align flex items

回答2:

I solved this by checking to see if the element offset is greater than 0, since wrapped items get 'flexed' below. Here's my function:

isHidden(id) {
    let el = document.getElementById(id);
    return (el.offsetTop > 0)
}