Align 3 unequal blocks left, center and right

Question

I'm trying to align a top menu which consists of 3 blocks of content.

What I'm trying to achieve is this:

• block 1: left aligned
• block 2: centered horizontally
• block 3: right aligned

If all 3 blocks were the same size, I could use flexbox (as in the snippet), but they're not, so it doesn't produce the output I require.

Instead, flexbox puts equal space between the 3 blocks - resulting in the middle block being aligned off-center.

I was wondering if this could be achieved with flexbox, or if not, another solution. This needs to work robustly in production so a 'Grid' solution is not applicable as there is insufficient support.

.container {
  margin: 20px 0;
}

.row {
  background-color: lime;
  display: flex;
  justify-content: space-between;
}

.item {
  background-color: blue;
  color: #fff;
  padding: 16px;
}

<div class="container">
  <div class="row">
    <div class="item">left, slightly longer</div>
    <div class="item">center, this item is much longer</div>
    <div class="item">right</div>
  </div>
</div>

Answer 1

You can consider flex-grow:1;flex-basis:0% for the left and right elements then use text-align to align content inside. I have added an extra wrapper to keep the background only around the text.

The trick is to calculate the free space by removing only the middle content and split it equally to the left and right element.

.container {
  margin: 20px 0;
  padding-top:10px;
  background:linear-gradient(#000,#000) center/5px 100% no-repeat; /*the center*/
}

.row {
  background-color: lime;
  display: flex;
  color: #fff;
}

.item:not(:nth-child(2)) {
  flex-basis: 0%;
  flex-grow: 1;
}

.item:last-child {
  text-align: right;
}

.item span{
  background-color: blue;
  display:inline-block;
  padding: 16px;
  border: 2px solid red;
  box-sizing:border-box;
}

<div class="container">
  <div class="row">
    <div class="item"><span>left, slightly longer</span></div>
    <div class="item"><span>center, this item is much longer</span></div>
    <div class="item"><span>right</span></div>
  </div>
</div>

You can also do the same by keeping the element close. Simply adjust text-align:

.container {
  margin: 20px 0;
  padding-top: 10px;
  background: linear-gradient(#000, #000) center/5px 100% no-repeat; /*the center*/
}

.row {
  background-color: lime;
  display: flex;
  color: #fff;
}

.item:not(:nth-child(2)) {
  flex-basis: 0%;
  flex-grow: 1;
}

.item:first-child {
  text-align: right;
}

.item span {
  background-color: blue;
  display: inline-block;
  padding: 16px;
  border: 2px solid red;
  box-sizing: border-box;
}

<div class="container">
  <div class="row">
    <div class="item"><span>left, slightly longer</span></div>
    <div class="item"><span>center, this item is much longer</span></div>
    <div class="item"><span>right</span></div>
  </div>
</div>